Abstract： The inhibitory activity of various concentrations of oleanolic acid (OA) on ovarian carcinomas IGROV1 and breast cancer cell line MDA-MB-231 were evaluated by using cell proliferation restrained, and MTT was used to measure the cells viability. The results showed that OA could significantly inhibit the viability of the ovarian carcinoma cells IGROV1 and MDA-MB-231 breast cancer cell line, comparing with the control group. IC50 values of tumor cells were 36.58 ?g/mL and 38.8 ?g/mL (P<0.01). Therefore, Oleanolic acid could inhibit the two malignant tumor cells viability and inhibitory activity of OA to ovarian carcinomas IGROV1 was higher than to breast cancer cell line MDA-MB-231.