Abstract: The size of pits in discharge machining affects the consistency of surface morphology, and the recast layer on the surface affects the quality of the surface. Based on the short electric arc-electrochemical hybrid machining（SEACM）method, a single discharge experiment was carried out on titanium alloy TC4 under two common SEACM power sources. The effects of different electrical parameters and different concentrations of NaCl solution on pit diameter, depth and protrusions height were studied, and the pit formation and electrochemical dissolution were simulated. The results show that the diameter and depth of the pit increase with the increase of voltage and pulse width, while the height of the bulge increases first and then decreases. The changes of pit diameter and bulge height under DC power supply are consistent with those under pulse power supply, but the pit depth first increases and then decreases with the increase of voltage. When the concentration of NaCl solution increases, the pit gradually decreases, and the removal rate of recast layer along the outer edge of the pit is highest,which is 19.9% at 10% processing concentration.