Objective To explore the relationship between plasma level of high-molecular-mass adiponectin (HMM-ADPN, H-ADPN) and macrovascular diseases in patients with type 2 diabetes mellitus. Methods A total of 106 patients with type 2 diabetes admitted in our department and Department of Endocrinology from December 2010 to December 2012 were enrolled in this study. These patients were divided into type 2 diabetes group (group A, n＝66) and type 2 diabetes accompanied with macrovascular complications group (group B, n＝40). Their height, body mass index (BMI), blood pressure and high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), triglycerides (TG), total cholesterol (TC), hemoglobin A1c (HbA1c), fasting blood glucose (FBG), fasting insulin (FINS), high-sensitivity C reactive protein (hs-CRP), total-adiponectin (ADPN), H-ADPN, carotid intima-media thickness (CIMT) and other indices were measured and calculated. And the results were compared between the 2 groups. Results Plasma H-ADPN was significantly lower in group B than in group A (P＜0.05). Multivariate regression analysis revealed that serum level of H-ADPN level was positively correlated with that of HDL-C (P＜0.05), but was negatively correlated with systolic blood pressure and CIMT (P＜0.05) after adjustment for age, gender, BMI and hs-CRP. Conclusion Plasma H-ADPN level might play an important role in the atherosclerosis in type 2 diabetes patients, and be involved in the incidence and development of macrovascular complications in them.