Asphalt Pavement was damaged more seriously in longitudinal Gradient than common segment because of its special load bearing conditions. This paper establishes a 3D Visco-elasto-plastic Finite Element to analyses the stress respond of pavement structure, calculating the discipline of stress behaviors under different gradient. Burgers model was used to study the factors which can influence on tracking, for example longitudinal Gradient, speeds and frequency of axle load. Result of calculation show that the maximum shear stress grows as the gradient increases. Rutting of pavement was small before a certain number of axle loads, but when beyond the certain number, the rutting incense notably, and the slower speed the vehicle has, the deeper tracking the pavement responds.