Abstract: The size of the discharge craters affects the consistency of the machined surface topography, and the height of the bump and the recast layer of the craters have important effects on the quality of the machined surface. In this paper, based on the short electric arc-electrochemical hybrid machining method, a single discharge experiment was carried out on titanium alloy TC4 under two common power supply types, DC and pulse, and the size and influence rule of single discharge craters in the short electric arc-electrochemical hybrid machining under two power supply types were analyzed. The variation of plasma discharge channel during arc discharge is studied by combining the waveform collected from single discharge crater experiment with the simulation model of arc discharge process. The results show that the difference of the size and influence law of DC and pulse discharge craters is related to the arc breaking mode, and the different arc breaking mode affects the plasma discharge channel. Dc arc tends to break through the movement of fluid medium and the change of electrode distance, while pulsed arc breaks through the change of voltage and electrode distance after pulse. These two arc breaking methods not only affect the size and morphology of the craters, but also affect the electrochemical corrosion effect after arc breaking.