To study the walking gait of lower extremity exoskeleton, a simulated numerical man model named by HL1 was built, and its gait was planned. An optim i zation algorithm to solve the gait function, which combined the solution of forw ard kinematics and inverse kinematics at the precondition of forward and sidewar d coupling movement, was proposed to ensure stability of HL1 and avoid any hit to the actuators and minimize the impact between the foot and the ground while w alking. This solution overcame the deficiency of the former method. Finally, th e numerical man model walked stably when simulated in the env ironment of Matlab & Adams based on the algorithm. It proves that this method is practicable.