Abstract: In order to study the effect of gait parameters, swing foot trajectory and body trajectory on gait stability and energy consumption of multi-legged robot a composite gait optimization method for a multi-legged robot based on optimal energy consumption was proposed，which transformed the gait optimization process into two nested sub optimization problems. Firstly，a body trajectory planning method based on zero moment point stability theory was given. The body trajectory was planned according to the next footholds and the supporting polygon. The body trajectory was continuous, smooth and stable with respect to the zero moment Point (ZMP)  stability theory. Secondly, a periodic gait optimization method based on energy consumption index was proposed. In order to optimize the walking gait, the virtual prototype model of quadruped robot was established as the gait optimization model, and the gait parameters，the swing foot trajectory and the body trajectory were optimized simultaneously. Finally，the virtual prototype simulation platform of the quadruped robot was built，and the simulation results show that the energy consumption of the robot is reduced by about 14% through the gait optimization algorithm.

Key words: multi-leggedrobot, gait optimization, foot trajectory, zero momentpoint, virtual prototype model