Abstract: The paper theoretically analyzed energy transfer progress of robot, obtained efficiency equation of every link of energy transfer progress , and established comprehensive energy efficiency model of robot. It also got the relationship among the efficiency, current and battery capacity through Matlab simulation, drew following conclusions: battery capacity has little impact on energy efficiency of robots, output current determines energy efficiency of the robot, when the output current is 20 A, the robot has maximum energy efficiency. The conclusion could provide the theoretical basis for establishment of energy consumption model of robot, battery capacity determination and power management.