Aim To clarify the content of antioxidant vitamins and oxidative property in small dense low density lipoprotein (sLDL) and to explore the role of small dense low density lipoprotein in lipid peroxidation of vascular endothelial cell. Methods Small dense low density lipoprotein was obtained by two sequential gradient ultra centrifugation and observed by negative staining electron microscopy; the content antioxidant vitamins such as vitamin A,alpha tocopherol (vitamin E) and beta carotene were measured by high performance liquid chromatography (HPLC). Continuously monitor small dense Low density lipoprotein susceptibility curve at absorbance 234 nm mediated by Cu 2+ . After exposure to small dense low density lipoprotein in vascular endothelial cell the malondialdehyde was measured. Results The small dense low density lipoprotein was isolated successfully. Compared with large buoyant low density lipoprotein, vitamin A,alpha tocopherol (vitamin E) and beta carotene and total antioxidant capacity of sLDL was 65%, 39% and 24% respectively lower and its lag phase was 37.5% lower, but its thiobarbituric acid reacting substances (TBARS) was 1.7 higher, while the the propgagtion phase was 1.28 longer. The malondialdehyde (MDA) content in culture media of 50 mg, 100 mg and 150 mg sLDL groups in 24 hour were significantly higher than those of the same dosage of large buoyant Low density lipoprotein (p<0.05). Conclusion The results suggest sLDL has strong effects on pathogenesis of atherosclerosis which may be related to decreased antioxidant content and antioxidation property and increased susceptibility to oxidation, as well as promoting peroxidation injure of vascular endothelial cell.