Objective To study the effects and the mechanisms of extract from a leguminous plant (Ammopiptanthus mongolicus cheng f.) (JA1) in northwest China on inducing apoptosis and inhibiting proliferation of HepG2 hepatocarcinoma cell in vitro. Methods The HepG2 cell line was used as target cells. The effect of JA1 on HepG2 cell growth was detected by microculture tetrazolium assay (MTT), flow cytometry assay, DNA agarose gel electrophoresis and transmission electronic microscopy. The expressive effect of the wt-p53 in HepG2 cells was analyzed with p53 protein test-reagent. Results JA1 not only had significant anti-proliferative effects depending upon time and dosage, but also induced apoptosis of HepG2 cells. Apoptotic typical morphological changes were observed in JA1-treated HepG2 cells under transmission electronic microscope, “Sub-G1” phase peak occurred in flow cytometry and DNA “ladder” was found in DNA agarose gel electrophoresis. The expression of the wt-p53 increased in vitro, and JA1-treated HepG2 and the positive cell percentage of the wt-p53 protein also increased. Conclusions JA1 could obviously induce apoptosis and inhibit proliferation of HepG2 cells in vitro, and these effects are closely related with the increase of wt-p53 expression. JA1 can be used as a good source of medicinal plant for the treatment of hepatocarcinoma. Objective To study the effects and the mechanisms of extract from a leguminous plant (Ammopiptanthus mongolicus cheng f.) (JA1) in northwest China on inducing apoptosis and inhibiting proliferation of HepG2 hepatocarcinoma cells in vitro. Methods The HepG2 cell line was used as target cells The effect of JA1 on HepG2 cell growth was detected by microculture tetrazolium assay (MTT), flow cytometry assay, DNA agarose gel electrophoresis and transmission electronic microscopy. The expressive effect of the wt-p53 was analyzed with p53 protein test- Results JA1 not only had significant anti-proliferative effects depending upon time and dosage, but also induced apoptosis of HepG2 cells. Apoptotic typical morphological changes were observed in JA1-treated HepG2 cells under transmission electronic microscope, “Sub-G1” phase peak occurred in flow cytometry and DNA “ladder” was found in DNA agarose gel electrophoresis. The expression of the wt-p53 increased in vitr and JA1-treated HepG2 and the positive cell percentage of the wt-p53 protein also increased. Conclusions JA1 could induce apoptosis and inhibit proliferation of HepG2 cells in vitro, and these effects are closely related with the increase of wt-p53 expression JA1 can be used as a good source of medicinal plant for the treatment of hepatocarcinoma.