The coprecipitate of anordrin (AD)-PVP was prepared by solvent method. The DSC (differential scanning calorimetry) revealed that AD did not have crystalline structure in coprecipitates of 1:7-1:9. X-ray diffraction spectrum of 1:8 coprecipitate (COPPT) showed no crystalline structure of AD. The dissolution rate of AD was about 38 times higher for 1:8 COPPT than pure AD. Activation energies determined by DTG (derivative thermogravimetry) were 182.8 and 133.4 kJ/mol, respectively, showing that the 1:8 COPPT is much more stable than pure AD in thermal degradation. The experimental results showed that anti-implantation effect of the 1:8 COPPT was much better than that of AD tablets: the number of implantation sites of mice administrated 1:8 COPPT (5 mg/kg) was 0.2 (P less than 0.01) and that of mice administrated AD tablets (10.6 mg/kg) was 0.9 (P less than 0.05); effective dose of 1:8 COPPT was less than half of that of AD tablets.