【Abstract】Objective To study the effects of arsenic trioxide (As2O3) on inhibiting the proliferation of hepatic carcinoma cell lines. Methods To detect the inhibiting rate of As2O3 and other 6 kinds of anticancer drugs (such as, NOV, ADM, MMC, 5-Fu, DDP and CTX) on hepatic carcinoma cell lines BEL-7404 and SMMC-7721 by using MTT assay. Results As compared with other 6 kinds of anticancer drugs, the inhibiting rate of As2O3 was the highest one (P＜0.01 or P＜0.05). The inhibiting rates of As2O3 in the groups with the concentration above 1.0 μg/ml were no different (P＞0.05). Conclusion As2O3 could inhibit hepatic carcinoma cell lines BEL-7404 and SMMC-7721 effectively in vitro. Drug sensitivity tests of different concentration’s As2O3 should be done in order to select the minimal and effective concentration of arsenic trioxide and reduce the side effects of arsenic trioxide.