Objective: To investigate the effects of ulinastatin on inflammation reaction and postoperative cognition disorders (POCD) in patients undergoing cardiac valve replacement surgery. Methods: Total 42 patients undergoing cardiac valve replacement therapy with cardiopulmonary bypass(CPB) were randomly divided into two groups. Group U(n = 21):the patients received ulinastitin 12 000 U/kg before incision by intravenously pumping,6 000 U/kg ulinastatin was added to the priming solution,and 6 000 U/kg ulinastatin was given before 5 min of the aortic decamping. Group C (n = 21):the control group was used the same dose of saline. Blood plasma concentrations of IL-6,IL-10,TNF-α and S100β concentration were determined before incision (T1),10 min after CBP (T2),30 min after CBP (T3),1 h after CBP (T4),3 h after CBP (T5),24 h after CBP (T6). Cognition state of every patient was evaluated by minimental state examination (MMSE) at 1d before operation and 3d after operation to record the number of the incidence of POCD. Results: The plasma concentrations of IL-6,IL-10,TNF-α and S100β of two groups at each time point of T2 to T6 were significantly higher than those at T1 point,(P < 0.05);Compared to Group C,the plasma concentrations of IL-6,TNF-α,S100β in Group U were significantly lower and IL-10 in Group U was higher at each time point of T2 to T6(P < 0.05);The incidence of POCD in group C (7 patients) was significantly higher than that in group U (2 patients) (P < 0.01). Conclusion: Prophylactic of ulinastatin in patients undergoing the cardiac valve surgery can decrease the incidence of POCD. The possible mechanism was that ulinastatin could cut down the relationship between inflammatory reaction in CBP and POCD.