Objective: To explore the changes of sex hormones and serum osteocalcin (OC) level in obese male patients with type 2 diabetes mellitus (T2DM) and their correlation with insulin resistance (IR). Methods: 100 obese male patients with T2DM who were admitted in our hospital were enrolled as T2DM group; 45 healthy males with similar age who underwent physical examination in the hospital during the same period were enrolled as control group. The general clinical data of all the subjects were recorded. The level of sex hormone were detected, including follicle stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2) and testosterone (T). The level of OC, fasting blood glucose (FBG), 2-hours postprandial blood glucose (2hPBG) and fasting insulin (FINS) were detected. The homeostasis model assessment of insulin resistance (HOMA-IR) was calculated. Pearson correlation analysis was used to analyze correlations between sex hormone, OC level and HOMA-IR. Results: The FBG, 2hPBG, FINS, HbA1c, HOMA-IR and E2 of patients in T2DM group were significantly higher than control group (P<0.05); While the OC level and T level were significantly lower than control group (P<0.05). The E2 level of obese male T2DM patients was positively correlated with HOMA-IR (r=0.172, P<0.05); While the T level and OC level were negatively correlated with HOMA-IR (r=-0.166, -0.216, P<0.05). Conclusions: The level of OC, E2 and T of obese male T2DM patients are related to IR. Improving OC and sex hormones levels in obese male T2DM patients may be of positive significance for improving IR and relieving disease.