Objective: To explore the role of vitamin D in the pathogenesis of initial type2 diabetes mellitus (T2DM) by comparing the difference of blood serum 25-hydroxy-vitamin D[25(OH)D],clinical and biochemical indexes between initial T2DM and normal persons. Methods: Sixty-five patients with T2DM were enrolled and divided into T2DM A group and T2DM B group according to the level of serum 25 (OH)D, and 32 healthy people were selected as control. The levels of serum 25 (OH)D,clinical and biochemical indexes were compared between two groups, and the difference of relative indexes including waistline,BMI,SBP,DBP,FBS,HbA1C,PTH were compared. Results: The level of serum 25(OH)D in the case group was significantly lower than that in the control group. Serum 25 (OH)D was nagetively related to BMI,TG,Apo-A1 and PTH,and was positively related to HDL-C. There was no relationship between hypovitaminosis D and blood pressure,glucose or HbA1C. Conclusion: The level of serum 25(OH)D in the patients with initial T2DM was low,especially with obesity and abnormality in blood-fat. There was no relationship between serum 25(OH)D and blood pressure,glucose, calcium or glycosylated hemoglobin. The reason that T2DM patients were easily complicated by hypertension was possibly related to the rise of PTH, and the mechanism is expected to study.