Abstract: Temper bead TIG welding of SA508-3 steel with weld overlap was studied. The result shows that there were obvious scallops between the adjacent welds when the overlap arrange from 0 to 30%, which was easy to form the lack of fusion problem. When the overlap excess 70%, the weld surface turns to tumor which was bad to deposit subsequent welds, which resulted in that the temper bead welding technique cannot be carried out. Welds surface was relatively flat when the overlap arrange from 40% to 60%, the micro hardness and hardening microstructures distribute uniformly.