Aim To investigate the possible mechanisms by which high-density lipoprotein （HDL） lead to the development of atherosclerosis by analysing the properties changes of HDL from the patients with hypercholesterolemia and its influence on vascular function. Methods 20 patients （male11, female9, aged from 18 to 60 years old） with hypercholesterolemia were selected as hypercholesterolemia group and 20 healthy adults （male12, female8, aged from 18 to 60 years old） were chosen as control group. The plasma concentration of total cholesterol （TC）, triglyceride（TG）, low density lipoprotein cholesterol（LDLC） and high density lipoprotein cholesterol（HDLC） were measured. The inflammatory level of HDL was analyzed. HDL was isolated from the plasma and was incubated with the aortic of C57BL/6 mice to observe the vascular contraction and vasodilation. Results In patients with hypercholesterolemia, the plasma concentration of TC（6.49±0.76 mmol/L vs 4.67±0.34 mmol/L, P<0.05）, TG（3.16±1.85 mmol/L vs 1.27±0.53 mmol/L, P<0.05）, and LDLC（4.52±0.70 mmol/L vs 2.98±0.40 mmol/L, P<0.05） were significantly higher than that in healthy subjects. However, the plasma concentration of HDLC（1.28±0.41 mmol/L vs 1.16±0.23 mmol/L, P>0.05） had no significant difference between hypercholesterolemia group and control group. The inflammatory level of HDL in patients with hypercholesterolemia（RFU:1104.0±182.5 vs 366.2±84.5, P<0.05） was significantly increased compared with the controls. This proinflammatory HDL dramatically inhibited the endothelium-dependent vasodilation. Conclusions HDL in hypercholesterolemia not only turned to inflammatory states and lost its effect on protecting cardiovascular function, but impaired endothelium-dependent vasodilation. Proinflammatory HDL may be one of the key factors in promoting the formation of atherosclerosis.