In order to simulate the contact state of actual pavement structure layer more accurately,fractal characteristic theory and interlayer contact theory are used in combination to establish the interlayer contact model,and the microcosmic structure state of asphalt pavement of flexible base is analyzed.Meanwhile,according to grading,interlayer contact area critical value between surface layer and base layer is calculated,and a quantitative method based on grading is also put forward to calculate the contact area of pavement structure.Thus the relationship between pavement microstructure and pavement performance may be analyzed clearly through this method.