Objective To investigate bone turnover markers and associated factors in the middle-aged and elderly men with type 2 diabetes mellitus (T2DM) and osteoporosis. Methods According to the 1998 WHO diagnostic criteria for osteoporosis and the 1990 WHO diagnostic criteria for diabetes, 80 middle-aged and elderly men were divided into osteoporosis group (OP, n=40) and diabetic osteoporosis group (DOP, n=40). All the patients received tests for bone turnover markers, serum calcium (Ca), serum phosphor(P), parathyroid hormone(PTH),25-OH vitamin D (25OHD) and other biomarkers of glucose metabolism. Statistical analysis was done using SPSS statistics 22.0. Depending on data type, Student′s t test, Pearson linear correlation or multivariate regression was performed. Results There were no obvious differences between the OP and DOP groups in BMD of L1-4[(0.960±0.281) vs (0.970±0.126)g/cm²,P=0.22], femoral neck [(0.895±0.162) vs (0.895±0.119)g/cm²,P=0.99] and total hip [(0.784±0.143) vs (0.748±0.112)g/cm², P=0.85].Compared with OP group, DOP group had lower osteocalcin (OC) [(16.69±8.91) vs (22.71±13.12)ng/ml,P=0.019], P1NP [(43.04±20.29) vs (53.64±24.08)ng/ml,P=0.037] and 25OHD [(12.80±5.54) vs (16.58±8.00)ng/ml,P=0.044], but higher CTX [(0.64±0.22) vs (0.49±0.30)ng/ml,P=0.013], the differences being statistically significant. Correlation analysis found that OC and P1NP were negatively correlated with HbA1c and the duration of diabetes, and that CTX was positively correlated with HbA1c and the duration of diabetes but negatively correlated with BMD of total hip (P<0.05). Regression analysis showed that HbA1c was an independent risk factor for OC and P1NP, and that CTX was affected by HbA1c and BMD of total hip. Conclusion Patients with T2DM have decreased bone formation and increased bone absorption which was gradually exacerbated with the deterioration of blood glucose and progression of diabetes. Vitamin D deficiency is worse in patients with diabetic osteoporosis.