In order to improve the positioning stability of tethered multi-rotor unmanned aerial vehicle (UAV), a domestic backup power supply based on supercapacitor is designed to meet the requirements of safe landing of tethered multi-rotor UAV when the ground power supply is abnormally cut off. The standby power supply consists of a main control unit, a charging unit, a discharging unit, an equalizing unit and a super capacitor bank, wherein the main control unit monitors the running state of the super capacitor bank in real time, and the charging, discharging and equalizing units respectively control the charging, discharging and equalizing processes of the super capacitor bank. The results show that the standby power supply has the characteristics of wide temperature adaptability, maintenance-free, simple structure and high localization rate, and can be effectively applied to tethered multi-rotor UAV equipment.