Abstract: In view of the typical cases of welding between weldments of different metal materials by surfacing isolation layer between low-alloy heat-resistant steel and low-alloy high-strength steel (the two weldments have different heat treatment systems), low-alloy heat-resistant steel and austenitic stainless steel (the first weldment needs heat treatment, the second weldment does not need heat treatment), and low-alloy heat-resistant steel (the two weldments have the same heat treatment system) in the process of pressure equipment manufacturing, through the formulation of reasonable welding process and heat treatment system, the welding problems between dissimilar metal materials have been successfully solved. The results indicate that the quality of welded joints can be guaranteed by selecting the correct isolation layer welding material and using the method of overlaying the isolation layer under different heat treatment systems. The successful application of the case provides a basis for developing reasonable welding processes for similar products.