Objective To investigate the predictive value of mild renal insufficiency on the endpoint events in patients with acute coronary syndrome (ACS).Methods A total of 552 patients with ACS were enrolled in the present study.According to the levels of estimated glomerular filtration rate (eGFR),patients were divided into two groups,normal renal function (eGFR≥90 ml · min-1 · 1.73 m-2) and mild renal insufficiency (60≤eGFR ＜90 ml · min-1 · 1.73 m-2).The primary and secondary events were collected and analyzed through the present prospective follow-up study.Results The patients in mild renal insufficiency group had a higher incidence of the primary endpoint events than normal renal function group [31 cases (12.6％) vs 15 cases (4.9％),P =0.001].There was no difference of the secondary endpoint events incidence in the two groups.The incidence rate of all-cause mortality [8.9％ (22 cases) vs 2.2％ (7 cases),P ＜0.001] and cardiac death [6.5％ (16 cases) vs 1.3％ (4 cases),P =0.001] was higher in mild renal insufficiency group,but there was no statistical difference of incidence rate of no fatal stroke and myocardial infarction in the two groups.The results of COX regression analysis showed that the incidence of primary endpoint events in patients with mild renal dysfunction was 2.265 folds (95％ CI 1.076-4.771,P=0.031) of patients with normal renal function.Further analysis indicated that the predictive value of mild renal insufficiency was only for all-cause mortality (HR 3.118,95％ CI 1.197-8.125,P =0.020),not for heart failure and revascularization.According to the Kaplan-Meier curves results,the incidences of the primary endpoint events (P =0.004) and all-cause mortality (P =0.001) were higher in mild renal insufficiency group than in normal renal function group.Conclusion Mild renal insufficiency has important predictive value for primary endpoint events in patients with ACS.