Abstract: In order to improve motion performance of quadruped robot,the phenomenon of swing-leg retraction(SLR)in the motion process was discussed.First,a robot model based on spring-loaded inverted pendulum (SLIP) was built and the impacts of SLR rate on energy loss,friction and impulse were analyzed respectively.Then the comprehensive optimal SLR rate to multi-objective was calculated unified objective method. And an appropriate Bezier trajectory for the study object was planned according to this optimal SLR rate.Simulation experiments show that the optimization of SLR rate is significantly beneficial to robot performance in the aspect of energy loss,friction and impulse.