Abstract： Objective To investigate the protection function of ulinastatin for kidney after ischemia-reperfusion in patients undergoing prosthetic valve replacement. Methods Eighty patients undergoing prosthetic valve replacement were randomly divided into two groups : UTI group (n = 40) and control group ( n = 40). In UTI group, UTI (8000 ～ 10,000)U/kg body weight was added in the priming solution and UTI (8000 ～ 10,000)U/kg body weight intravenously was applied in the first three days after operation. In control group normal saline was given. Blood and urine samples were taken before operation, on the 1st, 3rd, 5th and 7th day after operation. Serum croatinine (Cr) , urea nitrogen (BUN), urinary atom albumin (UAE), serum and urinary β2-microglobulin (β2-MG) were detected. Results There were no significantly differences among all indexes between two groups before operation(P 0.05). All indexes in two groups increased after operation. In UTI group , serum BUN and urinary β2-MG on 1st, 3rd and 5th , serum Cr and β2-MG on 1st, 3rd, and serum UAE on 1st day were all significantly lower than those in control group( P <0.05 ). Conclusion Ulinastatin provides remarkable protection for kidney after ischemia-reperfusion in patients undergoing prosthetic valve replacement.