For the robot with flexible manipulators, a rigid-flexible coupling dynamics model was established based on the Jourdain variation principle. Assumed model method was used to transform physical coordinate to modal coordinate, and to decouple the dynamics equations. According to adult arm size, ADAMS was adopted to built virtual prototype for simulation. The element interpolation function was designed. An algorithm was programmed using MATLAB to solve dynamics equations. And angle curves of manipulator obtained by ADAMS and MATLAB were compared. In view of four kinds of material: carbon fiber, aluminum, polyethylene and polypropylene, swing simulation of manipulators were done under the gravity. Figures and tables quantitatively described displacement of end deformation, spectrum and first-order and second-order vibration modal. And deformation and modal parameters were contrastively analyzed. The results show that the natural frequency of the manipulator increases and the transverse displacement of the manipulator end decreases as the ratio of the elastic modulus and density increases. Carbon fiber can be approximately modeled as a rigid body; carbon fiber and aluminum material are suitable for humanoid robot body parts; polypropylene has better integrated performance of the stiffness and flexible. The dynamics and solving method are proper.