The mechanism of vehicle shimmy has been paid much attention in the past decades. In which, the clearance of the steering linkage is usually neglected. Yet the prior research of the authors proved that the clearance can make great effects on the dynamic performance of the linkage. Therefore, based on nonlinear dynamics, a six-DOF dynamic model of vehicle shimmy system with consideration of the clearance was established. In which, the nonlinearity due to clearance of the movement pair in steering mechanism was taken into account. Numerical examples showed that the clearance of the movement pair could make great effects on the dynamic behavior of the vehicle shimmy system, and it is one of the key factors leading to chaos motion of the shimmy system, which provided theoretical basis for vehicle shimmy control.