Starting with the welding problems of UNS N08800 and A182 F11 CL.3 dissimilar steels in the construction of a large start-up furnace project,aiming at the contra-dictory welding characteristics of ferritic alloy steel and iron nickel alloy materials and the structural characteristics of these two materials in the equipment,the tungsten gas shielded welding process methods of these two materials are discussed,the welding and post welding heat treatment processes are formulated,and the welding performance test is carried out.According to the test results,a practical process scheme is developed,the key points of quality control in the welding process are clarified,and the construction problems are solved.