Objective To investigate the significance of 25 hydroxyvitamin D3 (25 (OH)D3) in patients with type 2 diabetes mellitus by comparing the differences of serum 25-hydroxyvitamin D levels between type 2 diabetes mellitus patients and healthy people.Methods One hundred and forty-seven patients with type 2 diabetes mellitus were selected as the T2DM group,and 135 healthy people were selected as the normal control (NC) group.The level of serum 25 (OH) D3 was detected by ELISA.Clinical data were recorded and biochemical indexes were also detected.Statistical analysis was performed.Results (1) Serum 25 (OH) D3 level in T2DM group was low,but there was no significant difference between two groups((23.10 ± 1.59) μg/L vs.(23.11 ± 1.65) μg/L; t =0.064,P =0.949),as well as between men and women in the 2 populations (T2DM men vs.women(23.22 ± 1.54) μg/L vs.(22.95 ± 1.65) μg/L; t =0.209,P ＞0.05; NC men vs women(23.03 ± 1.73) μg/L vs.(23.18 ± 1.59) μg/L; t =0.436,P ＞0.05) ; (2)The prevalence of vitamin D insufficient and deficiency in T2DM group was high,but it was not statistically significant between two groups (98.0％ vs.94.8 ％ and 2.0％ vs.5.2％ ; x2 =2.034,P =0.154) ; (3) Serum 25 (OH) D3 in T2DM group has a significant negative correlation with triglycerides (r =-0.218,P ＜ 0.01).Conclusion (1) Vitamin D level was low in both the healthy and T2DM populations in the southern region of China,the prevalence of vitamin D insufficient and deficiency was up to 90％.(2)Triglyceride is the only independent risk factor to T2DM population.