1. An accuracy traceability method based on precision coordinate control network for wMPS(workshop Measurement Positioning System), comprising the following steps: Step 1: providing N SMR nests and M stations in the measurement space and arranging a laser tracker ( 201 ) in station 1; Step 2: arranging an SMR ( 202 ) on SMR nest 1 to form a global control point 1, measuring 3-d coordinates of global control point 1, and by the same manner, moving the SMR( 202 ) to SMR 2, SMR 3. .. until SMR N−1 and SMR N respectively to measure the 3-d coordinates of global control point 2, global control point 3. .. until global control point N−1 and global control point N; Step 3: arranging the laser tracker ( 201 ) on station 2, station 3. .. until station M−1 and station M in sequence, and repeating the step 2 after each time the laser tracker ( 201 ) is moved, thus obtaining measurements for all the global control points via all the stations and in the step 2 and step 3, the laser tracker ( 201 ) must measure at least 3 global control points at each station; Step 4: calculating the positions (locations and orientations) of stations according to the 3-d coordinates of all global control points at all stations, thus obtaining initial iteration values of 3-d coordinates of all the stations and global control points; Step 5: using the range value from station to global control point measured by the laser tracker ( 201 ) as a constraint to establish optimization goal equation for adjustment calculation; by using the dynamic weighting method, tracing the measurement accuracy of 3-d coordinates of global control points to that of the interferometer range measurement of the laser tracker ( 201 ), thus establishing the precision coordinate control network; wherein the detailed steps of establishing the precision coordinate control network comprise: Step 5-1: according to the 3-d coordinates of global control points in individual station coordinates, calculating the range value r ij of the laser tracker; wherein, i represents the i th station, i=1,2,. .. , M; j represents the j th global control point, j=1,2,. .. , N; Step 5-2: taking the coordinates of station 1 as the global coordinates to calibrate each stations, and calculating the 3-d coordinates of global control points (x j 0 y j 0 z j 0 ) and station (x i 0 y i 0 z i 0 ) of the laser tracker in global coordinates, which are taken as the initial values during the optimization process; Establishing redundant range equations in global coordinates, the formula is expressed as follows: 
 l ij =√{square root over (( x j −X i ) 2 +( y i −Y i ) 2 +( z j −Z i ) 2 )}  (1) Wherein, l ij is range value, formula (1) is expanded by (x j 0 y j 0 z j 0 ) and (X i 0 Y i 0 Z i 0 ) via first order Taylorseries expansion to obtain: l ~ ij = l ij 0 + ∂ l ij ∂ X i ⁢ Δ ⁢ ⁢ X i + ∂ l ij ∂ Y i ⁢ Δ ⁢ ⁢ Y i + ∂ l ij ∂ Z i ⁢ Δ ⁢ ⁢ Z i + ∂ l ij ∂ x j ⁢ Δ ⁢ ⁢ x j + ∂ l ij ∂ y j ⁢ Δ ⁢ ⁢ y j + ∂ l ij ∂ z j ⁢ Δ ⁢ ⁢ z j ( 2 ) Wherein, (Δx j Δy j Δz j ) and (ΔX i ΔY i ΔZ i ) are the corrected values of 3-d coordinates of global control points and station of laser tracker respectively; the following error equation is established by formula (2): 
 vl ij =Ĩ ij −r ij (3) For M stations of laser tracker and N global control points, the redundant error equations are expressed as followings: 
 V=AΔX−b (4) Wherein, matrix A is a large sparse matrix expanded by formula (1) via first order Taylor series expansion, and 
 Δ X =[ ΔX 1 ,ΔY 1 ,ΔZ 1 ,ΔX 2 ,ΔY 2 ,ΔZ 2 ,. .. , ΔX M ,ΔY M ,ΔZ M ,Δx 1 ,Δy 1 ,Δz 1 ,Δx 2 ,Δy 2 ,Δz 2 ,. .. , Δx N ,Δy N ,Δz N ] T 
 b =[ r 11 −l 11 0 ,r 12 −l 12 0 ,. .. r MN −l MN 0 ] T ; Step 5-3: weighting the vector V according to the range accuracy σ l of laser tracker, the formula is expressed as follows: 
 P =diag((σ l l 11 ) −2 ,(σ l l 12 ) −2 ,. .. (σ l l MN ) −2 )  (5) Step 5-4: Initial weighting the vector [Δx 1 , Δy 1 ,. .. , Δx N , Δy N , Δz N ] T according to the range and angle accuracy of the laser tracker, and initial weighting the vector [ΔX 1 , ΔY 1 , ΔZ 1 ,. .. , ΔX M , ΔY M , ΔZ M ] T according to the calibration accuracy, thus obtaining initial weight matrix P X 0 of vector ΔX; Step 5-5: if the number N of global control points and the number M of stations of laser trackers meet the requirement of MN>3(M+N), establishing optimization object formulas of: { V T ⁢ PV = min Δ ⁢ ⁢ X T ⁢ P X 0 ⁢ Δ ⁢ ⁢ X = min ( 6 ) Performing iteration calculating with the singular value decomposition and generalized inverse matrix method; Calculating vector ΔX k and covariance matrix Q x k in each iteration, indexed by k; and correcting the P X 0 according to the Q x k to achieve dynamic weighting; Performing iteration until the end condition is satisfied, thus obtaining the 3-d coordinates of global control points and completing the establishment of precision coordinate control network; Step 6: arranging and initializing a plurality of transmitters( 101 ), and then calibrating the transmitters in combination with the precision coordinate control network to establish the measurement network; Step 7: measuring the global control points and measured points simultaneously by using wMPS(workshop Measurement Positioning System), and using the 3-d coordinates of global control points as the constraint for adjustment calculation to obtain the 3-d coordinates of the measured points, and finally tracing the obtained 3-d coordinates of the measured points to the precision coordinate control network.