The invention discloses a closed-loop aircraft fuel tank airborne inerting system. The system comprises an oil tank, the gas outlet of the oil tank is connected with the inlet of a condenser through apipeline, and the gas outlet of the condenser is sequentially connected with a first flame arrester, a gas dryer, a first flow sensor, a gas compressor and the gas inlet of an electric pressure regulating valve through pipelines. The gas outlet of the electric pressure regulating valve is sequentially connected with a first heat exchanger, a first pressure sensor and a first temperature sensor through pipelines, and the other end of the first temperature sensor is connected with the inlet of a first electric stop valve and the inlet of a second electric stop valve. An outlet pipeline of the first electric stop valve is connected with the inlet of a conventional hollow fiber membrane separator, and an outlet pipeline of the second electric stop valve is connected with the inlet of an emergency hollow fiber membrane separator. According to the present invention, the compensation loss increase caused by the engine bleed air can be avoided, the system weight and size are small, the inerting requirements under different working conditions are met, mode switching is achieved, and the system work is more intelligent.