In order to study deeply the Exhaust gas recirculation（EGR）performance of marine diesel engines，a venturi high-pressure exhaust gas recirculation device was established to overcome the exhaust gas reflow problem in a certain type turbocharged diesel engine. With the device, the EGR performance test is accomplished and an optimal EGR decision-making optimization method based on grey correlation coefficient modified is proposed. The results show that the venturi tube EGR can basically meet the injection requirements of high-pressure exhaust gas and makes good results to the diesel engine . Through the venturi tube EGR, the NOX emissions reduces significantly with the maximum drop of 30.6%. The explosive pressure in cylinder reduces with the EGR rate increases, and the cylinder pressure curve shows a single peak at low-speed conditions and double peaks at high-speed condition. However, the fuel consumption rate, NO, and smoke have been negatively affected. Due to small samples, the traditional evaluation method is difficult to determine the optimal EGR rate reasonably, while the proposed method can effectively solve this problem. It can weaken the shortcomings of subjective judgment and greatly improve the rationality of decision-making results.