Protective effects of API0134 on endothelial cells (EC) damaged by oxidatively modified low density lipoprotein (oxLDL) were studied. The results showed that the content of endothelia (ET) and malondialdehyde (MDA) in the media of porcine aortic EC incubated with oxLDL were increased and the cGMP was decreased significantly, and the activity of superoxide dismutase (SOD) was inhibited. The effect of cytotoxicity of oxLDL can be eliminated by API0134. These results suggest that API0134 may protect EC against damages elicited by oxLDL.