Abstract: Aiming at heavy-haul vehicles, the paper investigates the characteristic of dynamic interaction between wheel and rail due to the hunting motion by considering them in a whole system. On the condition of the vehicle operating speed being a little higher than its nonlinear critical speed, the wheel/rail vibration motion is simulated. In this case, the contact point of the wheel and rail occurs at the wheel tread or the wheel flange periodically, causing a sharp change in the lateral force of wheelset. The maximum lateral force is nearly 10 times larger than the normal value without hunting motion. Due to the existing of that force, the wheel shifts from the left side to the right side with a main frequency of 11.25Hz and a larger yaw angle, and the maximum shift is 15mm, as is called hunting motion with a hunting wave of 3.4m. Meanwhile, the lateral displacement of rail is very obvious, resulting in more serious oscillation of wheelset. It is noticeable that the main frequencies of the lateral force and the rail lateral displacement are consistent with the frequency of hunting motion of the wheel.