a thermo - sensitve copolymer of following formula ; is disclosed ; wherein r 1 is hydrogen , or — c — r 2 ; r 2 is c 7 - 30 alkyl substituted or unsubstituted with functional groups ; r 3 is hydrogen , or c 1 - 6 alkyl ; and x , y or z individually is an integer greater than 0 . the thermo - sensitive copolymers disclosed here are easy to be implanted into a human body through injection . the biodegradability is greatly improved and the cytotoxicity of the copolymers is low .