〔Abstract〕 Objective To study the effect of human oxidized low density lipoprotein(OxLDL) on rat vascular endothelium-dependent relaxation and its mechanism. Methods Acetylcholine(ACh)-induced endothelium-dependent relaxations of rat coronary artery(CA) and mesenteric artery(MA) were examined by using examination of vascular tone; nitric oxide(NO) and H2S concentrations in supernatant of cultured human coronary artery endothelial cells(HCAECs) were measured by commercial kit; store-operated calcium entry(SOCE) in HCAECs were measured by using fluorescent dye Fura-2 Am. Results 100 mg/ml OxLDL pretreatment markedly decreased ACh-induced endothelium-dependent relaxation of rat CA and MA; pretreatment of OxLDL 100 mg/ml for 24 h significantly inhibited the production of H2S rather than NO in the HCAECs; OxLDL significantly inhibited the release of Ca2+from the store and subsequent SOCE in HCAECs. Conclusion OxLDL could damage rat vascular endothelium-mediated vasodilation, and its mechanism may be related to the inhibitions of H2S production and SOCE in endothelial cells.