Abstract: The effect of welding thermal cycle on the microstructure and properties of the intercritically reheated coarse grained heat affected zone(IC-CGHAZ) was studied using thermal simulation technology. The results showed that the formation of fine martensite along the prior austenite grain boundaries deteriorating the performance of IC-CGHAZ. The IC-CGHAZ is the weakest area in the welded joint. The impact toughness of the joint was improved significantly allowing the joint have a good match in hardness and toughness when the IC-CGHAZ experienced a thermal cycle with peak temperature of 400- 650℃.The microstructure and properties of IC-CGHAZ can be improved effectively by precisly controlling the layer thickness and the welding thermal cycle conditions in SA508-3 steel multi-pass welding processing.