Abstract: In this study．calf aortic endothelial cells(ECs) were cultured in vitro to study the ECs damages induced by exogenous oxygen free radical(OFR)，and the protective effects of ginseno- sides．Exogenous OFR was generated by three methods：enzyme reaction(xanthine—xanthine oxidase)，chemical reaction(Cu²⁺-ascorbate)and electrolysis．The experimental results indicated that the xanthine--xanthine oxidase method is most suitable for the study of free radical mediated ECs damages．Addition of ginsenosides(40 ul·ml^-1 )reduced the concentration of MDA in the cultured ECs．while the 6-keto-PGF_1a content in the medium was reduced(P>0.05)and the morphologic damages of the ECs was alleviated．It is concluded that ginsenosides exerted a protective effects on ECs damages against lipid peroxidation，and ginsenosides might play an important role in antiatherosclerosis through its protective effect on endothelial cells．