A method based on MATLAB programming to establish two robots system simulation model was proposed. Firstly, connecting rod coordinates of four and six degree of freedom (DOF) robots in two robots system were built respectively according to DH parameters. Then coordinate relationship between each rob of the two robots system was determined. Secondly, transformation matrices of the end effectors were calculated while two robots system operating. Thirdly, two robots system model was established via MATLAB programming, and trajectory of robots was planned according to assembling steps as required. Results analyses of trajectory planning show simulation model can reflect the actual position, orientation and trajectory of the robot system.