A dynamic model, including the driver inputting module, the road model and the vehicle model with 22 degrees of freedom (DOFs), was proposed for the four-axle vehicle driven by in-wheel motors. The 22 DOFs, which represented the dynamic characteristics of the vehicle, were consisted of 6 DOFs of the vehicle body and 16 DOFs of the vertical and rotation motion of 8 wheels. Based on the deduced equations, a computer simulation model was established with highly modular approach in Matlab/Simulink software. The simulation tests, including the handling stability and the riding comfort, were performed on the 22 DOFs model and the ideal 2 DOFs linear vehicle model under the same driving condition. The simulation results reveal that the proposed model is able to legitimately describe the dynamic characteristics in various conditions. What's more, the dynamic characteristics, especially riding comfort, are deteriorated because of the increased unsprung mass.