The auxiliary power unit (APU) is an important system of the civil aircraft for the aircraft safety and comfort. Large current output for long time will cause disadvantage effect on battery usage life. Also the too long start time will damage APU. So when start the APU by using the battery as the input power, for the purpose of reducing the damage to battery and APU, it is needed to start the APU in a shorter time by a lower battery output current. The subsection of power-current control strategy can start the APU in shorter time with the lowest damage to the battery and APU. This is important for extending the use life of APU and battery.