Abstract: Due to the application of a large number of power electronic equipments on the aircraft，the aircraft

power supply network tends to be complicated，and thus there is an urgent need to effectively evaluate the power

quality of the power supply network. In order to evaluate AC power quality of aircraft，a comprehensive evaluation

method of AC power quality based on rough set theory was proposed，the evaluation of 115 V/400 Hz AC power

quality on typical passenger aircraft was realized. It can be seen from the study results that the weight ranking of each evaluation index obtained in the proposed method can meet with the index weight ranking obtained by other

methods，and the power quality evaluation results can accurately reflect the operating status of the aircraft AC power system. It shows that the evaluation method based on rough set theory can obtain reasonable weights of aircraft AC power evaluation indicators based on objective measurement data，thereby to realize the effective evaluation of aircraftAC power quality and overcome the uncertainty brought by subjective evaluation steps in other methods.

      Key words: multi-electric aircraft；power quality；rough set；knowledge reduction；weight