Abstract: A hybrid 3D processing system based on build-up welding and electrolytic machining was established in this paper, which involved an arc welding robot, a digital welder and electrolytic machining device. Rough cast was built up by the robot, and then modified by the electrolytic device to get dimensional accuracy. A processing path planning called screw overlap method was developed to deal with the collapse of welding bead. Using sodium chloride and monarkite solution as electrolyte can make mild steel and aluminum alloy workpiece with a smooth surface. Finally, the as-prepared products possessing dimensional accuracy and smooth surface was manufactured by the build-up welding and electrolytic machining hybrid processing system.