Abstract: For the coordinated movement of three branches robot, the method of separating influence coefficient is used to separate the Jacobian matrix and inertia matrix of each branch of the robot. The Jacobian matrix and inertia matrix of the whole robot system may be reconstituted by separating the influence coefficient. So the kinematics and dynamics equations can be set up. The method of multiplier penalty function is utilized to optimize the least joint driving moment of the three branches robot. The singular value decomposition of matrix may be avoided, and the calculational stability may be improved. Iteration is used to calculate the question and to simplify the solving process.