the present invention will be illustrated with reference to the specific examples . those skilled in the art will appreciate that these examples are only intended to illustrate the present invention without limiting the scope of the present invention in any way . the experimental methods in the following examples are all conventional methods unless expressly stated ; the experimental materials used in the following examples are all purchased from conventional biochemical reagent stores unless expressly stated . 10 . 0 g daidzein and 25 ml anhydrous pyridine were dissolved in 400 ml acetone to obtain a first mixed solution , and the first mixed solution was stirred mechanically and maintained at 0 ° c ., and then added slowly with 27 . 3 chloroacetyl chloride dropwise , after completion of dropping , the first mixed solution was kept at 0 ° c . and continued to react for 2 h , and then warmed naturally to room temperature and continued to react for 2 h , and then the first mixed solution was sampled and detected by tlc ( v ( petroleum ether ): v ( ethyl acetate )= 1 : 1 ), the result of detection indicated that the reaction was complete . the mixture after the reaction was filtered , and the filter cake was washed with water to make the ph value achieve ph = 7 . 0 , and then dried under vacuum to give 12 . 0 g 7 - o - chloroacetyl daidzein , with a yield of 93 %. at room temperature , 8 . 8 g 7 - o - chloroacetyl daidzein prepared in example 1 , 12 . 0 g potassium carbonate and 10 . 0 g potassium iodide were dissolved in 300 ml acetone , and the mixture was stirred mechanically and then added with 20 ml diethylamine , and then the resulting mixture was heated to 80 ° c . and reflux was performed for 4 h , tlc ( v ( petroleum ether ): v ( ethyl acetate )= 1 : 1 ) indicated that the reaction was complete . the mixture was cooled , filtered and washed by acetone during filtration , and the filtrates were combined , washed and concentrated , then added with 20 ml acetone and continued to be distillated until no liquid is contained thereinto , then added with 40 ml anhydrous ethanol and 6 . 0 g anhydrous sodium sulfate and dried overnight . filter , introduce dry hcl gas into the filtrate until no solid was precipitated . the mixture was filtered and recrystallized with anhydrous ethanol , and dried under vacuum to give 8 . 6 g solid of white powder , with a yield of 80 %. 1 hnmr ( 400 mhz , d 6 - dmso ): 10 . 65 ( s , 1h , h - 4 ′), 8 . 46 ( s , 1h , h - 2 ), 7 . 98 ( d , 1h , j = 8 . 8 hz ), 7 . 68 ( d , 2h , j = 8 . 6 hz , h - 2 ′, h - 6 ′), 7 . 32 ( d , 2h , j = 8 . 6 hz , h3 ′, h - 5 ′), 6 . 97 - 7 . 02 ( m , 2h , h - 6 , h - 8 ), 4 . 52 ( s , 2h , nch2c ═ o ), 3 . 31 ( q , 4h , j = 7 . 2 hz , — ch 2 ch 3 ), 1 . 30 ( t , 6h , j = 7 . 2 hz , — ch 2 ch 3 ). esi - ms : m / z = 368 . 15 [ m + 1 ] + , 406 . 10 [ m + 39 ] + . first , sodium bicarbonate and sodium hydroxide in an amount based on the above prescription were weighed and dissolved in water for injection , cooled to below 5 ° c . through an ice - water bath , and then the sample of example 2 in an amount based on the above prescription was added and dissolved , and the ph value of the mixture was adjusted to 7 . 5 through sodium hydroxide solution , filtered and lyophilized to obtain the lyophilized powder . in the water bath at 25 ± 5 ° c ., the solvent equilibrium experiment was performed on the above materials for at least 20 hours by using 1 ml methanol , then the solution was filtered and dried in the air for 10 minutes , and after the solvent was evaporated under vacuum , the approximate solubilities of the above materials in the solvent was measured through gravimetric analysis , with results shown in table 1 . i ) tested drug : lyophilized powder prepared in example 3 , which is dissolved with distilled water when administered in vivo , and dissolved with saline when administered in vitro , and respectively prepared into solutions with desired concentrations . ii ) experimental animals : wistar , which is a male rat outbreeding closed system , purchased from the institute of laboratory animal sciences , chinese academy of medical sciences , weighing 242 ± 11 . 2 g , the animals are divided into 5 groups with 10 animals in each group . 1 . rat in vitro general artery - jugular vein blood flow in the bypass method ( please refer to “ journal of changchun university of traditional chinese medicine ”, 2011 , volume 27 , issue 4 , pages 514 - 518 , yunfei sun , min shi , “ study on the effect of pueraria injection on thrombosis formation , cerebral ischemia and platelet aggregation in rats ); 2 . in vitro thrombosis instrument method ( please refer to “ acta academiae medicinae primae shanghai ”, 1979 , volume 6 , issue 3 , pages 205 - 206 , chengzhu li , shichun yang , fengdi zhao , “ simple in vitro thrombosis apparatus and measuring method ”). iv ) dose design , calculated according to the effective dose of 7 - o — n , n - diethyl - aminoacetyl daidzein hydrochloride : 1 . experiment in vivo : the dose is 50 mg / kg , 100 mg / kg , 200 mg / kg , and the animals are administered intragastrically once daily at 1 ml / 100 g mouse for 3 consecutive days ; 2 . experiment in vitro : the dose is 1 . 56 mg / kg , 3 . 12 mg / kg , 6 . 25 mg / kg , and the animals are administered once directly . 1 . blank control , the animals are administered with the same volume of distilled water in the experiment in vivo ; and administered with the same volume of saline in the experiment in vitro ; 2 . positive control , the animals are administered with acetylsalicylic acid ( produced by northwest second synthetic pharmaceutical factory ) at 45 mg / kg in the experiment in vivo . the antithrombotic effects of 7 - o — n , n - diethyl - aminoacetyl daidzein hydrochloride are shown in table 2 and table 3 : it can be seen from the results of table 2 and table 3 that 7 - o — n , n - diethyl - aminoacetyl daidzein hydrochloride prepared by the present invention has a good antithrombotic effect . ii . experiment 2 — effects of compounds on hypoxia tolerance of mice at normal pressure compound in u . s . pat . no . 6 , 121 , 010a ( hereinafter referred to as “ usp compound ”) 70 mice were taken and randomly divided into seven groups , except the blank group which was not administered and the saline group which was administered with the same volume of saline , the remaining five groups were respectively injected intraperitoneally with 25 mg / kg pueraria daidzein , 36 mg / kg compound of the example of the present application , 47 mg / kg 4 , 7 - disubstituted daidzein , 36 mg / kg 4 - substituted daidzein and 36 mg / kg usp compound ( the converted dose of each compound is equivalent to the dose of the daidzein , since the daidzein is difficult to dissolve in water , 50 % propylene glycol aqueous solution is used to dissolve , and other compounds were dissolved with water to achieve a suitable concentration ), 20 min after administration , the mice were put into a 250 ml grinding jar ( where 10 g soda lime was placed ), with one mouse in each jar , and the jar was capped tightly after the mouse was put into the jar , then the survival time of the mice was immediately recorded by a stopwatch . the results are shown in table 4 . it can be seen from the results of table 4 that the compound of the example can significantly prolong the hypoxia tolerance time of the mice , and has better effect compared with the daidzein , and the poor effect of the daidzein may be caused by incomplete absorption after administration due to its poor solubility in water . other compounds for comparison have weak effects . this may be relevant to the fact that the compounds are difficult to be hydrolyzed into the daidzein to play an effect after entering the blood vessels . iii . experiment 3 — effects of compounds on acute cerebral ischemia in mice 70 mice were taken and randomly divided into seven groups , except the blank group which was not administered and the saline group which was administered with the same volume of saline , the remaining five groups were respectively injected intraperitoneally with 25 mg / kg pueraria daidzein , 36 mg / kg compound of the example of the present application , 47 mg / kg 4 , 7 - disubstituted daidzein , 36 mg / kg 4 - substituted daidzein and 36 mg / kg usp compound ( the converted dose of each compound is equivalent to the dose of the daidzein , since the daidzein is difficult to dissolve in water , 50 % propylene glycol aqueous solution is used to dissolve , and other compounds were dissolved with water to achieve a suitable concentration ), 20 min after administration , the mice were decapitated rapidly from behind the ear , then the time starting from decapitation to the last gasp was recorded . the results are shown in table 5 . it can be seen from the results of table 5 that the compound of the example can significantly prolong the acute ischemia tolerance time of the mice , and has better effect compared with the daidzein , and the poor effect of the daidzein may be caused by incomplete absorption after administration due to its poor solubility in water . other compounds for comparison have weak effects . this may be relevant to the fact that the compounds are difficult to be hydrolyzed into the daidzein to play an effect after entering the blood vessels . iv . experiment 4 — effects of compounds on euglobulin lysis time : antithrombotic effect research 1 30 guinea pigs were taken and randomly divided into five groups , each group was administered intragastrically with 25 mg / kg pueraria daidzein , 36 mg / kg compound of the example of the present application , 47 mg / kg 4 , 7 - disubstituted daidzein , 36 mg / kg 4 - substituted daidzein , and 36 mg / kg usp compound ( the converted dose of each compound is equivalent to the dose of the daidzein , since the daidzein is difficult to dissolve in water , 50 % propylene glycol aqueous solution is used to dissolve , and other compounds were dissolved with water to achieve a suitable concentration ), 1 . 5 ml blood was taken from the heart before administration , and after 7 consecutive days of administration , 1 . 5 ml blood was taken from the heart 30 minutes after the last administration , and put into a sodium citrate anti - cruor tube , and the plasma was separated by centrifugation , then 0 . 5 ml plasma was taken and added with 9 ml distilled water and 0 . 1 ml of 1 % acetic acid solution , and the mixture was centrifugated after being refrigerated for 30 minutes , then the resulting precipitate was dissolved with 0 . 5 ml sodium borate buffer ( ph9 . 0 ), and the dissolution time was recorded as euglobulin lysis time , it can be obtained through calculation that fibrinolytic enzyme activity ( u )= 10000 / optimal dissolution time ( min ). the results are shown in table 6 . it can be seen from the results of table 6 that the daidzein has weak antithrombotic effect after oral administration . this is mainly because the daidzein is difficult to be adsorbed by oral administration . the compound of the example improves the solubility of the drug as well as the blood concentration , thus having significant efficacy . other compounds have poor effects probably due to absorption , hydrolysis and other reasons . 30 rabbits were taken and randomly divided into five groups , each group was administered intragastrically with 15 mg / kg pueraria daidzein , 22 mg / kg compound of the example of the present application , 28 mg / kg 4 , 7 - disubstituted daidzein , 22 mg / kg 4 - substituted daidzein and 22 mg / kg usp compound ( the converted dose of each compound is equivalent to the dose of the daidzein , since the daidzein is difficult to dissolve in water , 50 % propylene glycol aqueous solution is used to dissolve , and other compounds were dissolved with water to achieve a suitable concentration ), 2 ml blood was taken from the heart before administration , and after 7 consecutive days of administration , 2 ml blood was taken from the heart 30 minutes after the last administration , and injected immediately into the rotating ring of the thrombosis instrument , and rotated at 15 - 17 rpm under 37 ° c ., and the rotating time of the thrombus alone with the ring was recorded , which is defined as thrombus formation time of fibrin , the rotation was stopped after 15 minutes , the thrombus was taken out , and the length of the thrombus was measured . the results are shown in table 7 . it can be seen from the results of table 7 that the daidzein has weak antithrombotic effect after oral administration . this is mainly because the daidzein is difficult to be adsorbed by oral administration . the compound of the example improves the solubility of the drug as well as the blood concentration , thus having significant efficacy , the thrombus formation time is significantly extended and the length of the thrombus is obviously shortened . other compounds have poor effects probably due to absorption , hydrolysis and other reasons . the above are detailed description of the daidzein derivative and pharmaceutically acceptable salt thereof provided by the present invention . the present invention illustrates the principle and embodiments of the present invention through specific examples , and the descriptions of the above examples are only intended to help understand the method and its core concept of the present invention . it should be noted that , those of ordinary skill in the art can make a number of improvements and modifications on the present invention , without departing from the principle of the present invention , and these improvements and modifications also fall within the protection scope of the claims of the present invention .