In order to study influence of flexible rod on the dynamic characteristics of the spatial parallel mechanism, the 3-RRPaR spatial parallel mechanism with structural redundancy was taken as the research object, and a general method for establishing rigid flexible coupling dynamic model of redundant spatial parallel mechanism was proposed. A three-dimensional two node beam element model was established based on the absolute node coordinate method. The structural characteristics of the mechanism were studied, and the rigid flexible coupling dynamical equation of the mechanism was derived by Lagrange multiplier method. The generalized α method was used to solve the dynamic equation in Matlab, and the dynamical responses curves of the mechanism under different elastic modulus were obtained. It can be concluded that the flexible rod had an important influence on the output characteristics of the mechanism. The smaller the elastic modulus was, the greater the influence on the mechanism was, and the impact on the acceleration of the moving platform was the most significant. The research can provide a modeling method and idea for other rigid flexible coupling dynamics of other spatial parallel mechanisms, and also can lay a foundation for the dynamic modeling of the mechanism considering joint clearance and flexible rod at the same time.