Objective To study the effects of dioscin on Bel-7402 and LO2 cell proliferation and apoptosis and its possible mechanisms. Methods Bel-7402 and LO2 cells were exposed to 0. 5~ 16 μmol / L dioscin for 24 h, and inhibition of cell proliferation was examined via MTT assay. Morphologic changes in the cells were quantified using an inverted microscope, and Hoechst 33258 staining was used to observe morphological changes in the apoptotic cells. Changes in the mitochondrial membrane potential were measured using JC-1 staining. Bcl-2 and Bax expression were detected via western blot. Results Compared with the negative control group, Bel-7402 and LO2 cell proliferation was significantly inhibited dose-dependently after exposure to all concentrations of dioscin. The IC50 of the Bel-7402 cells was 2. 04 μmol / L; the IC50 of the LO2 cells was 2. 76 μmol / L. Compared with those of the negative control group, the cells showed varying degrees of distribution, density reduction, roundness, exfoliation, death and necrosis induced by 1 and 2 μmol / L of dioscin. The cell boundary was blurred and induced cell apoptosis. JC-1 staining result showed that the mitochondrial membrane potential was significantly decreased in both cell lines after treatment with dioscin ( P< 0. 01). Western blot result showed that dioscin significantly increased Bax expression and inhibited Bcl-2 expression in both cells lines ( P< 0. 05; P<0. 01). Conclusions Dioscin inhibited Bel-7402 and LO2 cell proliferation in vitro. The possible mechanism may have been that dioscin increased Bax expression, inhibited Bcl-2 expression, and induced apoptosis; thus, dioscin may induce liver injury during development of its anti-hepatocarcinoma functions.