Roughness of surface at different grades is generated by adopting SIMULINK toolbox and filtering white noise method . With the space of roughness being unchanged and the vibration amplitude of different level of roughness being equal, parameter selection in the process of generating white noise is discussed emphatically. Then a quarter landing gear taxiing model is established under condition of the influence of lift in consideration of the force of landing gear buffer and tire system. The statistical variation of wheel dynamic load coefficient at different speed and roughness level is simulated and studied. The results shown that the mean value of dynamic load coefficient has nothing to do with the grade of road surface roughness. The standard deviation of dynamic load coefficient increases continuously with the increase of running speed, but there exists the most sensitive speed related to the natural frequency of the system. The maximum value of dynamic load coefficient determined calculated by 3 criterion increases first and then decreases with the increase of running speed. With the uniform increase of IRI value, the cumulative relative displacement growth rate of landing gear model becomes smaller and smaller with the oil nonlinear damping being affected.