Abstract: In order to establish the non-linear fatigue damage evolution equation of asphalt mixture and the axial load conversion method of asphalt pavement, the aggregate gradation and optimum asphalt-aggregate ratios are determined by a proportion design of asphalt mixture. Then, the fatigue damage variable is defined by the modulus decay basing on the basic theory of damage mechanics. The fatigue damage equation was deduced. The direct tensile fatigue test results were fitted from using the fatigue damage equation. The regularities of model parameters and damage with a stress ratio are given out. The new axle load conversion method is established for asphalt pavement. The results indicate that the fatigue damage evolution has the apparent non-linear properties of asphalt mixture. The Miner linear fatigue damage theory is not suitable to describe the process of fatigue damage evolution for asphalt pavement. It is not safe to use the axial load conversion method deriving from the Miner equation. The new axial load conversion method basing on the nonlinear fatigue damage evolution can consider the influence of loading history and damage history.