In this paper, a multi-legged gait prototype robot with four legs consisted of redundant joint is conducted. To control any motion for the four legged robot with redundant joint, the authors propose an optimal control system with fusing the attitude motion and the translation motion by performance index even if constrain condition has strong nonlinearity and number of control input variables is different from number of control output variables. Then to verify the proposing optimal method, the robot having four legs with 4 redundant DOF is treated and three case numerical simulations of optimal fusion for attitude and translation are executed. Then obtained the result is evaluated.