OBJECTIVE：To study the effects of Plantago asiatica polysaccharide on the proliferation ，migration and invasion of breast cancer cells ，and to investigate its mechanism preliminarily. METHODS ：Using human breast cancer cell MDA-MB- 231 as subjects ，MTT method was adopted to detect the effects of different concentrations of P. asiatica polysaccharide（8，16，32，64 mg/L）on the cell proliferation ability ，and survival rate of the cells was calculated. Scratch test and Transwell invasion test were used to detect the effects of different concentrations of P. asiatica polysaccharide（8，16 mg/L）on cell migration ability and invasion ability. Western blot assay was used to detect the expression of epithelial-mesenchymal transition （EMT）-related proteins [matrix metalloproteinase- 2（MMP-2），MMP-9，E-cadherin，N-cadherin，vimentin]. RESULTS ：Results of MTT assay showed that survival rate of the cells in 32，64 mg/L P. asiatica polysaccharide groups were significantly lower than control group （P＜0.05 or P＜0.01），so that 8，16 mg/L，which did not affect the cell survival rate ，were used as the follow-up drug concentrations. Compared with control group ，relative mobility （12，24 h），relative invasion rate and relative expression of MMP- 2，MMP-9， N-cadherin and vimentin protein were decreased significantly in 8，16 mg/L P. asiatica polysaccharide groups （P＜0.05 or P＜ 0.01），while relative expression of E-cadherin protein was increased significantly （P＜0.05 or P＜0.01）. CONCLUSIONS ：P. asiatica polysaccharide can inhibit the proliferation of breast cancer cells MDA-MB- 231，and inhibit the migration and invasion of the cells by regulating the expression of metastasis and EMT-related proteins.