The application of multi-robot coordination in a merging system for posture alignment of huge and heavy parts is studied. The trajectory planning method of posture aligning and merging system for large parts with multiple 3-DOF robots is proposed. The coordinates transformation relationship between merging part and single robot is established on the basis of large parts merging technology. By using the redundancy of multirobot coordinated manipulation system and considering the constraints of payload, driving force and driving velocity, the trajectory planning strategy of robot in posture aligning and merging system for large parts is achieved on the basis of kinematic model and inverse kinematic algorithm.