OBJECTIVE： To investigate inhibitory effects of lupeol on the proliferation of human breast cancer MCF-7 cells and its possible mechanism. METHODS： Taking MCF-7 cells as research object， MTT assay was used to detect the proliferation of MCF-7 cells after treated with different doses of lupeol （7.5， 15， 30， 60， 90 mg/L） for 24 h. Survival rate and IC50 of MCF-7 cells were calculated. The inverted microscope and cell cloning experiment were used to observe and detect the morphological characteristics of MCF-7 cells and clonal colony formation after treated with different doses of lupeol （15， 30， 60 mg/L） for 24 h. The rate of clonal colony formation was calculated. MTT method and Western blotting assay were used to detect the proliferation of MCF-7 cells and the expression of related regulatory proteins （ERK1/2， p-ERK1/2， JNK， p-JNK， p38 MAPK， p-p38 MAPK） after additionally treated with MAPKs signaling pathway-related regulation protein inhibitors PD98059， SP600125 and SB203580. RESULTS： After treated with 15， 30， 60， 90 mg/L lupeol， survival rates of MCF-7 cells were decreased significantly （P＜0.05 or P＜0.01）. IC50 value of the compound was 52.94 mg/L. After treated with 15， 30， 60 mg/L lupeol， the morphological characteristics of cells in each group changed， and the phenomena of cell exfoliation， floating， solid shrinkage， roundness， volume reduction and necrosis were observed. The formation of clonal colony decreased and the rate of clonal colony formation decreased significantly （P＜0.05 or P＜0.01）. When lupeol used alone， compared with control group， survival rate （60 mg/L lupeol）of MCF-7 cells was decreased significantly； the expression of p-ERK1/2 （15， 30， 60 mg/L lupeol）， p-JNK （30， 60 mg/L lupeol） and p-p38 MAPK （30， 60 mg/L lupeol） were increased significantly （P＜0.05 or P＜0.01）. After additional use of relevant inhibitors， compared with 60 mg/L lupeol group， survival rates of MCF-7 cells in combination groups were increased significantly， while relative expression of p-ERK1/2， p-JNK and p-p38 MAPK were decreased significantly （P＜0.05 or P＜0.01）. CONCLUSIONS： Lupeol can inhibit the proliferation of human breast cancer MCF-7 cells， the mechanism of which may be related to the phosphorylation of MAPKs signaling pathway-related regulatory proteins.