Abstract: Objective To study the inhibition effect and mechanism of As₄S₄(Tetraarsenic Tetrasulfide)on ovarian cancer SKOV3 cells′ proliferation and cell apoptosis.Methods SKOV3 cell lines were treated with different concentration of As₄S₄,MTT method was used to examine the inhibition of SKOV3 cells by As₄S₄.Transmission electron microscope was used to observe morphologic change of apoptosis and flow cytometry(FCM)assay was performed to measure change of cell apoptosis rate and cell cycle.RT-PCR method and Westernblot was used to detect the mRNA and protein expression of Bcl-2 and Bax.Results SKOV3 cell proliferation was inhibited dependenting on time and concentration(P＜ 0.01).Flow cytometry(FCM)assay indicated that As₄S₄ could induce the apoptosis of SKOV3 cells,where cells in G₀/G₁ stage reduced,while cells in S stage increased.The expression of Bcl-2 was reduced,while the expression of Bax was increased.Conclusion As₄S₄ is effective to inhibit the proliferation of SKOV3 cells,and the mechanism might be relevant to induction of cell apoptosis and regulating the expressions of Bcl-2 and Bax.