Aimed at the problem of turbocharged diesel engine EGR (exhaust gas recirculation) performance evaluation and optimal EGR rate determination, especially in some cases with poor data because of the limit of conditions, an optimized multi-objective grey decision method based on grey theory and entropy weight is proposed. The internal combustion pressure ,fuel consumption rate, NOX ,CO and smoke degree were selected as the decision target, and the initial decision-making model was established based on traditional grey situation theory. According to the characteristics and optimization requirements of EGR, The optimal compromise between combustion and emission performance is proposed to transform into the decision-making target weight problem , then a subjective weight optimization method based on expert scoring and grey relational analysis is proposed. In addition, the entropy weight method was used to solve the subjective and objective weight vector and the optimized multi-objective grey situation decision making model was established, which can not weaken the human error of subjective empowerment, but also fully explore the intrinsic objective relationship of the evaluation index parameters. At last, an optimization simulation platform for EGR performance evaluation based MATLB/GUIDE is designed and established. The results show that the optimization simulation platform can effectively improve the efficiency of simulation calculation, which is more convenient for practical engineering applications; the optimized method can successfully solve the EGR performance evaluation and optimal EGR rate determination under different working conditions, the decision result is reasonable and consistent with the prevailing principle of the EGR determining, which provide a new research ideas for EGR performance optimization.