Abstract: Objective To investigate the correlation between the expression of serum 25 hydroxycholecalciferol ［25-(OH)VD］ and the occurrence of diabetic retinopathy(DR)in patients with type 2 diabetes mellitus(T2DM). Methods The clinical data of 188 patients with T2DM was retrospectively analyzed, the patients were divided into DR free group(n=132)and DR group(n=56)according to test results. The levels of 25-(OH)VD, glycosylated hemoglobin(HbA1c)and fasting blood glucose(FBG)in the two groups were detected, and the correlation between the expression of 25-(OH)VD and the occurrence of DR was analyzed. Results The level of 25-(OH)VD in the DR free group was significantly higher than that in the DR group, while the levels of HbA1c and FBG were lower than those in the DR group(P<0.05). Occurrence of DR was negatively correlated to 25-(OH)VD(r=-0.684, P<0.001), and positively correlated to levels of HbA1c and FBG(r=0.583, 0.621, P<0.001). Logistic regression analysis showed that the lower expression of serum 25-(OH)VD might be the influencing factor of DR(OR=1.836, P<0.05); the area under the curve(AUC)of serum 25-(OH)VD in predicting the occurrence of DR was more than 0.8, indicating a certain predictive value. Conclusion The expression of serum 25-(OH)VD in T2DM patients is closely related to the occurrence of DR. Therefore, it may participate in the occurrence and development of DR.