Objective To study the effects of acanthopanax giraldii harms var hispidus hoo polysaccharides (AGP) on proliferation and expression of nuclear transcription factor p53 and c-myc in human breast cancer cell line MDA-MB-231. Methods The proliferation rate of human breast cancer cell line MDA-MB-231, which was incubated by different concentration of AGP (0.15625, 0.3125, 0.625, 1.25, 2.5g/L) in DMEM medium for 1, 3, 5, 7 days in vitro respectively, was studied by WST-1 cell proliferation and cytotoxicity assay kit. The changes of human breast cancer cell line MDA-MB-231 morphology were observed by an inverted microscopy. The expression of apoptosis-related proteins such as p53 and c-myc was detected by fluorescence immunoassay and Western blotting. Results WST-1 assay showed that different concentration of AGP inhibited proliferation of human breast cancer cell line MDA-MB-231 treated for 3day, 5day, 7day when compared with the negative control group (P <0.05). The inhibition rate depended on AGP dose and reaction time. According to fluorescence immunoassay and Western blotting analysis, c-myc expression in cytoplasm reduced and p53 expression increased significantly after the treatment of AGP on human breast cancer cell line MDA-MB-231. Conclusion AGP has the effect of inhibiting proliferation on human breast cancer cell line MDA-MB-231.Its role may be related to reduce c-myc expression and increase p53 expression of human breast cancer cell line MDA-MB-231.