Based on the motion characters of the running cars, a novel coupling 4-UPS/UPR parallel mechanism is proposed as a car motion simulation platform. Based on the screw theory, the constraints of the middle constraint limb on the upper platform are analyzed. The singular, which is related to the configuration of the hinges, is analyzed using Grassmenn geometry. The kinematic operator function of the rotation matrix is employed to analyze the coupling motion characters of the parallel mechanism. The kinematic model of the mechanism is established using screw velocity and acceleration. The detailed dynamic model, including all the limbs, is gotten by the Newton-Euler Equation on rigid-body. And the corresponding numerical example is given to demonstrate the above theory.