In recent research, AC arc fault characteristic analysis is basically based on constant frequency system. The AC power supply of aircraft is developing towards the direction of variable frequency power supply, and the frequency range is 360—800 Hz. The characteristics extracted from constant frequency system, such as current change rate, the ratio of flat shoulder and harmonic component will change with frequency, which cannot be applied in variable frequency system. Therefore, this paper designs the AC arc fault experiment platform, and the serial and parallel arc faults are simulated under the condition of 115 V/360—800 Hz. Based on this, the change rule of arc current under different frequencies is analyzed. The characteristics of AC arc fault are studied in time domain and frequency domain respectively, then the standard deviation, odd harmonic and even harmonic are extracted as the characteristics of arc fault detection in the variable frequency system. Finally the effectiveness and feasibility of AC arc fault detection algorithm is designed and verified through experiment.