Abstract: Objective To observe the effect of ulinastatin on cognitive dysfunction after cardiac surgery in elderly patients. Methods A total of 71 cases of senile patients with cognitive impairment after cardiac surgery were studied,according to the admission,they were divided into observation group (36 cases) and control group (35 cases). Both groups were treated with the same routine therapy ,the cases in observation group were treated with ulinastatin, the cases in control group were treated with same amount of normal saline. The serum NSE (neuron-specific enolase) was monitored before and after operation, and evaluated by MMSE (brief mental state scale). To compare the difference of serum NSE and MMSE between the two groups before and after operation, and to evaluate the effect of ulinastatin on cognitive dysfunction after cardiac surgery in elderly patients. Results The serum NSE in the observation group was significantly lower than that in the control group. The difference was statistically significant (P< 0.05), and the postoperative MMSE score was better than that of the control group (P< 0.05). Conclusion Ulinastatin can reduce the expression of serum NSE and reduce the incidence of postoperative cognitive dysfunction in elderly patients with cardiac surgery.