Objective To prospectively study the difference of urinary N-acetyl-β-D-glucosaminidase( UN-AG) and retinol binding protein(URBP) in contrast-induced nephropathy (CIN). Methods The clinical data of 150 patients undergoing coronary angiography were documented. The urine and blood samples before,24 hours after and 48～72 hours after the procedure were collected;Serum creatinine (SCr) and urinary ereatinine (UCr)were tested by enzymic method. UNAG and URBP were tested by ELISA in CIN and control group. CIN was defined as an increase in SCr of ≥44 μmol/L or >25% from baseline 48 ～72 h after the procedure. 27 age- , sex- , results of coro-nary angiography-matched cases were taken as control group. Results CIN was diagnosed in 13 of 150 patients (8.7%). In CIN group, UNAG/UCr were significantly higher than that in control group[ 1.97 (1.06,2.64) U/mmol vs 1.07 (0, 68,1.88 ) U/mmol, Z = 2.076, P = 0.039 ] before ;24 hours after the procedure, UNAG/UCr was signifi-cantly up-regulated in CIN group from baseline level [ 2.82 ( 1.88 ,4.26) U/mmol vs 1.97 (1.06,2.64) U/mmol, Z =2.607,P =0. 009]. ROC curve analysis showed that baseline UNAG could be used as an early predictor for CIN, the AUC =0. 776 ,P =0.023 ;when cut off value = 8.08 U/L,the sensitivity and specificity of UNAG were 0. 771 and 0. 713 respectively. The percentage of patients of UNAG over 8.08 U/L in CIN group was significantly higher than that in control group[77.1% (10/13) vs 29.6% (8/27) ,Z =2. 564,P =0. 011 ] ,the related risk factor is 5.58,95% CI was 1.24 ～ 25.08. Conclusion UNAG could be used as a predictor of CIN before the procedure and its postprocedure 24 h level maybe useful in early diagnosis after the procedure.