According to the defects that the value of identification coefficient is obtained by an experience selection method in grey relational analysis, which affects the accuracy of assessment. A comprehensive assessment model is establis hed based on improved fuzzy gray relational analysis method. The influence of the value of identification coefficient on relational degree is analyzed and the common rules and the determining method are established, which can solve the quan tification problem of the value. The method of reasonable determinative differen tiation coefficient is adopted to determine improved correlation coefficient, then by using generalized weight distance of fuzzy mathematics theory, automobile braking system performance is evaluated and analyzed by means of the comprehensive evaluation methods of grey and fuzzy, the result proves the reliability and feasibility of the model.