According to special requirement of power system of rescue robot, three types of power supply were compared, which were lithium iron phosphate batteries, super capacitor and lithium iron phosphate batteries parallel connected super capacitor. It was found that the lithium iron phosphate battery had good properties as the robot's power. The models were established based on studies of the robot's discharge characteristics in low current. The energy efficiency and energy consumption of the lithium iron phosphate battery with 24 V and 40 A?h was analyzed and calculated. It was found that reducing the output current could reduce the self energy consumption of the battery and increase the output energy, and the self energy consumption of the battery could be controlled at the level under 12% when the discharging current was below 30 A.