In the process of short arc machining, the fluid software Fluent was used to simulate the gap flow field of different electrode diameters. The rule of chip removal was obtained indirectly through the pressure and velocity fields in the inter-electrode flow field, which was verified by experiments. The results show that the increase of electrode diameter can promote chip discharging from the machining gap and reduce the short circuit phenomenon caused by the accumulation of gap particles, thus avoiding the “secondary discharge”; when the processing depth remains unchanged, the size of electrode diameter is positively correlated with the removal rate of workpiece material, which proves that “area effect” is existed in short arc processing;the relative change of the electrode diameter has no obvious improvement on the surface quality of the workpiece, that is, the influence on the surface roughness is not significant.