Objective To observe the inhibitory action of annonaceous acetogenins AS-4 on human liver cancer cell line HepG2 in vitro. Method Using different concentration of annonaceous acetagenins group(6.25,12.5,25,50 ?g/mL),control group(25 ?g/mL) of masculine(DDP),control blank group,after routine culture of 24 or 48 hours,the effect of annonaceous acetogenins AS-4 on HepG2 was analyzed by colorimetry assay(MTT) and inverted phase-contrast microscope observing. Result AS-4 had the best inhibitory effect on HepG2,the highest inhibitory rate was 91.68%,and the effect was time-dosage dependent,and the 48 h IC50 was 6.67 ?g/mL. Conclusion AS-4 has lethal effect on HepG2 in vitro,and shows obvious cytotoxic effect.