Objective To study the diagnosis value of serum retinol binding protein (RBP),cystatin C(Cys C) and β2 microglobulin (β2-M) in early renal injures of gcstational diabetes mellitus (GDM) patients.Methods 85 case of GDM pregnant women admitted to Shiyan Maternal and Child Health-Care Hospital from Jan.2009 to Jan 2015 were chosen as research objects,and were divided into simple diabetes group (35 cases),micro proteinuria group (30 cases) and massive proteinuria group (20 cases) according to the urinary albumin excretion rate (UAER),while 30 cases of healthy pregnant women were recruited randomly during the same period as control group.The 24h urine protein,serum RBP and renal function indicators [blood urea nitrogen (BUN),creatinine (Ser),Cys C and β2 M],the positive rates of RBP,Cys C,β2-M and combined detection of RBP,Cys C,β2-M of the four groups were compared.Results The 24h urine protein in simple diabetes group,micro proteinuria group and massive proteinuria group were significantly higher than that in the control group (t=3.91～ 16.33,all P＜0.01),the difference between the 3 groups were statistically significant (t=6.78～ 16.94,all P＜0.01).The levels of BUN,Scr,Cys C,β2-M and RBP in micro proteinuria group and massive proteinuria group were significantly higher than those in control group and simple diabetic group (t=3.68 ～ 18.54,all P＜0.01),there were significant difference in above indexes between micro proteinurine group and massive proteinuria group (t=4.70～ 10.87,all P＜0.01).The positive rates of RBP,Cys C,β2-M and combined detection of RBP,Cys C and β2-M in micro proteinuria group and massive proteinuria group were significantly higher than those in control group and simple diabetic group (x2 =20.27～38.57,all P＜0.01).There was no significant difference in the positive rates between micro proteinuria group and massive proteinuria group (x2 =0.62～0.93,all P＞0.05).The positive rate of combined detection of the three indicators was higher than that of the single detection in the same group (x2=3.97～6.65,P＜0.05 or P＜0.01).Conclusion The detection of serum Cys C,RBP and β2-M has a high clinical value in the diagnosis of early renal damage in patients with GDM.The positive rate of combined detection of 3 indexes was higher than that of single index.