In order to reduce the phenomenon of spark discharge in short arc milling and ensure the stability of arc discharge state, the voltampere variation law of arc discharge was deduced through the expansion law of ion discharge channel and the energy conservation law. The arc discharge waveform was divided into three characteristic stages as the judgment basis of the arc discharge state, and the theory accuracy was verified through the discharge waveform. Combined with arc breaking mechanism, the geometric model of mechanical arc breaking was established, and the duration of single pulse arc was calculated, the influence of electrode speed on discharge was analyzed. The micromorphology and voltage and current waveforms under different arc duration were obtained through experiments. The results show that when the arc duration is maintained at 0.5 ms, the processing quality is better and the arc discharge stability is higher. The results provide a theoretical basis for ensuring the discharge stability in arc processing