Based on uniform design principles, 15 kinds of typical degrees of AC 20 asphalt mixture segregation gradation were simulated. The envelop areas between each segregation gradation curve and design gradation curve were calculated by composite trapezoidal integration. Combined with the physical, mechanical and pavement performance tests in laboratory, deviation degree of performance indexes for asphalt mixture was put forward. The correlations between deviation degree and envelop areas were established, all correlation coefficients were more than 09 which indicated that there are good positive linear relationship between deviation degree and envelop areas. The quantitative evaluation criterion was put forward in accordance with the envelope area. The test results for mechanical performance and extraction of asphalt mixture through field sampling on typical segregation regions show that all indexes deviation degree calculated by the envelope area are in 80% confidence interval of the deviation degree actually measured, it means that the envelope area evaluation criterion based on uniform design principles for quantitative assessment on the gradation segregation of the asphalt mixture is reasonable and feasible, which can provide the demonstration and reference for accurate evaluation of the asphalt pavement gradation segregation.