Objective:To study the correlation between serum proprotein convertase subtilisin/kexin 9 (PCSK9) and the risk factors of atherosclerosis (AS) in patients with type 2 diabetes mellitus (T2DM). Methods:Fasting blood samples were obtained from 351 T2DM patients enrolled in the department of endocrinology and metabolism of Jiangsu Province Hospital between January 2011 to November 2011. History-taking, physical and biochemical examinations, and the severity of carotid artery and artery of lower extremity atherosclerosis assessment were examined. Serum PCSK9 was measured with a sensitive and specific sandwich ELISA. Results:The level of serum PCSK9 in patients with T2DM combined with AS was higher than that in T2DM patients without AS (P < 0.05). Besides,there was also a positive correlation between serum PCSK9 and varied carotid AS related-index,such as RCCA inside diameter,RCCA PI,RICA PI,LCCA PI,LICA PI,RICA RI,LCCA RI (all P < 0.05). Furthermore,a negative association was found between the serum PCSK9 and RCCA Vmax,RCCA Vmin,RCCA Tamx, in this population (all P < 0.05). Conclusion:The level of serum PCSK9 is strongly correlated with several risk factors of AS. In combination with traditional risk factors of AS,serum PCSK9 will provide more information for predicting the presence of AS-related cardiovascular diseases.