Abstract: Objective 　To study the effect of antiprogestin mifepristone on cell cycle of endomet rial carcinoma. Methods 　Human endometrial carcinoma HHUA cell was cultured in vitro and t reated with mifepristone in different concent ration for 24-96 hours. Influence of mifepristone on the cell cycle dist ribution were detected by using flow cytometry ( FCM) . The expression of protein related cell cycle was observed by immunohistochemical. Results 　Treated HHUA cell in vit ro with mifepristone ≥5μmol/ L for 36 hours, rate of G1phase was increased and S-phase f raction (SPF) was decreased obviously ( P < 0. 05) . The expression of cell cycle related protein p21 and p16 were raised significantly ( P < 0. 05) . Conclusion Antiprogestins mifepristone could effectively block HHUA cells at G₁ phase and inhibit the proliferation by cont rolling the expression of protein related cell cycle.