Objective:To explore the inhibitory effect of arsenic troixide (ATO) on the growth of human endometrial cancer HEC-1-A cells in vitro and in vivo. Methods:Tetrazolium salt assay (MTT) was used to compare the inhibitory effect of ATO on HEC-1-A cells with that of progesterone, medroxyprogesterone acetate (MPA) and cisplatin (CDDP). Flow cytometry and DNA electrophoresis were used to determine the effects of ATO on cell cycle and apoptosis. Human endometrial cancer xenografted model was established in nude mice. The tumor-bearing nude mice were randomly divided into the experimental groups: ATO low dose group (4 mg·kg-1·d-1), medium dose group (6 mg·kg-1·d-1), high dose group (8 mg·kg-1·d-1), CDDP positive control group (3 mg·kg-1·d-1) and saline negative control group. The drugs were administered intraperitoneally for 14 consecutive days, and then the tumor volume and tumor inhibition rate were calculated. Results: ATO 1-20 μmol/L and CDDP markedly inhibited the cell growth. The inhibitory effect of ATO was higher than that of CDDP. ATO 5 μmol/L treatment induced apoptosis and arrested cells at S and G2/M phase. ATO 4, 6, and 8 mg·kg-1·d-1 and CDDP 3 mg·kg-1·d-1 inhibited tumor volume by 50.97%, 75.58%, 56.92%, and 52.23%, respectively; and inhibited the tumor weight by 10.15%, 29.33%, 16.67%, and 14.69%, respectively. The difference was significant compared with negative control group (P<0.05). Conclusion:ATO inhibited the growth of endometrial cancer cells HEC-1-A in vitro and in vivo. It may become a novel therapeutic reagent for the treatment of endometrial cancer.