This study presents a dynamic model for mobile manipulator which is focused on analysing the dynamic coupling of mobile platform and robotic manipulator. Since the robotic arm acts on the mobile platform directly, it is obvious that the shift of manipulator's center of mass has an impact on the mobile platform. In this study, the dynamics properties of robotic arm's center of mass are obtained over the theory of particle system. Then, the dynamic model, connected both the mobile platform and manipulator, is established. In order to verify the effectiveness of the proposed dynamic model, position based control works in combination with force control to guarantee that the involved mobile platform achieves locomotion accurately and compliantly. The experiment are carried out based on a mobile manipulator which is combined with UR5 manipulator and mobile platform. Analyses of the results are validated the correctness and availability of the proposed method.