Objective To investigate the serum levels of 25-hydroxyvitamin D3 (25 (OH)D3) and urine vitamin D binding protein(uVDBP) in patients with diabetic nephropathy (DN),and to determine the relationship between 25 (OH) D3,uVDBP and DN,in order to provide a new method for early diagnosis and treatment of DN.Methods From January 2015 to December 2015,85 DN patients admitted into Weihai Municipal Hospital were selected.According to the ratio of UALB to UCR(UACR),the patients were divided into three groups.Type 2 diabetes had 28 cases of normal albuminuria group,31 cases of microalbuminuria group,and 26 cases of clinical albuminuria group.We also enrolled 25 healthy people who received outpatient service as control group.Serum 25 (OH) D3 levels were measured by chemiluminescence method.Urine VDBP levels were assayed by ELISA.FPG,HbA1 c,UREA,SCr,TC,TG were measured by electrochemiluminescence.Results The results showed that serum 25 (OH)D3 was significantly lower in the normal albuminuria group,microalbuminuria group and clinical proteinuria group than that in the control group (P ＜ 0.05),and there was statistically significant difference among the four groups [(20.04 ± 7.52) ng/mL,(16.54 ± 6.51) ng/mL,(10.77 ± 4.63) ng/mL,(29.65 ± 5.47) ng/mL,F =86.294,P ＜ 0.001].The results showed that uVDBP was significantly higher in the DN group than that in the control group(all P ＜ 0.05),and there was statistically significant difference among the four groups [(8.44 ± 3.20) mg/L,(14.22 ± 3.26) mg/L,(2 1.77 ± 5.87) mg/L,(4.95 ± 1.34) mg/L,F =125.583,P ＜ 0.001].Correlation analysis showed that serum 25 (OH) D3 decreased gradually with the increase of DN and negatively correlated with UACR (r =-0.575,P ＜ 0.01),while uVDBP level was positively correlated with UACR (r =0.436,P =0.015).Conclusion With the progress of DN,serum 25 (OH) D3 levels gradually decreased,indicating that 25 (OH) D3 may play an important role in the pathogenesis of DN;uVDBP may be an early diagnostic method for DN.