Due to the merits of small size, high power density, high voltage, low self-discharge and low resistance, li-ion battery can replace traditional power battery and be used in AGV system. Over-voltage and low-voltage protection circuit, temperature protection circuit, equalizer circuit, self-locked circuit and voltage display circuit are designed; Equalization circuit can keep consistency of each cell used in the system; Self-locked circuit can make the system much more stability while the display circuit can ahcive the information of the power system. Experiments prove the effectiveness of these designs.