Abstract: Objective 　To examine the effect of arsenict rioxide (As2 O3>>) on cell proliferation and cell cycle arrest in the human ovarian carcinoma cell line SKOV3. Methods 　The SKOV3 cells were cultured in RPMI1640 with different concent ration of As₂O₃, and harvested in different cultured time. Methyl thiazolyl tetrozolium(MTT) was used to establish the dose-effect curves. Inverted microscope and transmission electron microscope were used to examine the morphologic changes of SKOV3 cells, and cell cycles and apoptosis were examined by flow cytometry ( FCM) . Results 　As₂O₃ could significantly inhibit SKOV3 cells proliferation with a time-and dose-dependent fashion. The SKOV3 cells could be arrested significantly at G₂ /M phase by As₂O₃ . There were typical apoptotic changes in each group under inverted microscope and transmission electron microscope. Conclusion 　As₂O₃ could obviously inhibit the proliferation of SKOV3 cells through inducing apoptosis and S 、G₂ / M arrest .