Objective To investigate the effect of vitamin D (VD) deficiency on the pathogenesis of Zucker diabetic fatty (ZDF) rats. Methods Male 5 -6 weeks old Zucker rats were randomly divided into 4 groups according to their body weight: normal control group (ZL), VD deficient control group (ZL + VD. Def), model group (ZDF) and VD deficient model group (ZDF + VD. Def). All the rats were fed to 12 weeks of age, and body weight, food intake, water intake, urine volume, urine glucose, fasting blood glucose were measured. The glucose tolerance was tested at 11 weeks. Pancreatic samples were taken and tissue sections were examined by pathology using HE staining. Results The body weight of ZDF + VD. Def group was higher than that of the ZDF group. Drinking water and urine volume were increased earlier than the ZDF rats. The blood glucose in the ZDF + VD. Def group was increased significantly earlier than ZDF group, it is about 2 times of the ZDF group at 12 weeks. Compared with the ZDF group, the impaired glucose tolerance and islet damage were more serious than the ZDF + VD. Def group. Conclusions Vitamin D deficiency accelerates and aggravates the pathogenesis of ZDF rats, and VD deficiency may be a key factor in the pathogenesis of obese DM Type 2.