In order to research the surface integrity of SEAM, the surface figure, surface heat-affected zones (HAZ ) and surface hardness are analyzed. The author mainly researches the influence factors of water pressure, air pressure, cathode feed rate and relative line speed on processing indictor. The orthogonal experiment results indicate that the main influence factors of surface roughness and HAZ are air pressure, gap voltage and cutting depth. In SEAM, certain scope pressure atomization of dielectric liquid has deionization and arc-extinguishing effect, and takes away melted metal and heat from the discharge channel in time. Workpiece surface will be smoothness. However, the enlarged air pressure will break normal electrode discharge and make the surface smoothness worse. The research of influence of gap voltage on surface quality are accomplished.