In order to get more accurate motion state parameters of vehicle driving simulator, the 7-DOF loop dynamic model and calculation model of vehicle are established firstly, and the second-order nonlinear ordinary differential equations with tire rolling angular velocity and steering angle of driving wheel as inputs and transverse longitudinal and yaw angle as outputs are obtained. Then, the second-order nonlinear ordinary differential equations are reduced. Finally, the fixed step length is set, and the parameters of vehicle motion state are calculated in turn. The simulation results show that the proposed method has higher accuracy, the maximum displacement error is only 0.0037m, the maximum speed error is only 0.02m/s, the maximum yaw rate and yaw angle error are only 0.0057 rad/s and 0.0047 rad respectively, and the computation time is reduced by 43.2% compared with the extended Kalman filter, which can greatly improve the fidelity of simulation driving.