Abstract This study aimed at the investigation of the effect of preheating on the residual stress and metallurgical properties of weldment. In this study, an autogenous gas tungsten arc welding was used on type 304 stainless steel. During welding, the thermal cycles of four locations in the weldment were recorded to investigate the behavior of thermal stress and residual stress. The residual stresses were determined by using the hole-drilling method of ASTM standard E837. The metallurgical properties were examined by using the optical microscope and Vickers hardness tester. The experimental results show that there are two factors influencing the formation of welding residual stress in preheat process: the elevation of welding equilibrium temperature and the increase of amount of heat input. The cumulative effects result in the welding residual stress not being improved significantly with preheating. The residual stress increases with the increase of preheat temperature. Preheating will induce a wider heat-affected zone and a poorer strength base metal than the conventional welding in type 304 stainless steel.