Abstract: The flexible manipulator dynamics is a topic of general interest in robotics, but the study on its cooperation is still in vacuum at present. Based on the kinematic and dynamic coordinated constraints, the dynamic model of flexible manipulator cooperation is obtained for the first time by using Finite Element Method and Lagrange Equation. The algorithm of its inverse dynamic problem is proposed and a numerical example of two planar 3-R flexible robots manipulating a rigid load is illustrated successfully.