Abstract: Objective The dissimilar steel joint between ethylene cracking furnace pipe and quenching unit mainly bears the pressure in running process of pipe. The aim of this paper is to select appropriate material and process of welding by process experiments. Methods Taking the welding wire of ERNiCrCoMo-1 as filling material, the manual tungsten inert gas welding process experiments between 25Cr35NiNbMA and 20Cr32NiNb alloy steel pipes are carried out, which are used in ethylene cracking furnace pipe and quenching unit, and the microstructure and properties of the joints are analyzed and tested. Results The microstructure of the dissimilar steel joints is austenite phases, and the strengthening phase are the granular Cb,Cr,Mo riched phase. The result of strength testing at high temperature indicates that the joints fracture at the base metal with the intergranular fracture mode.The strength, elongation and the stability of the joint meet the design requirement. Conclusion The referential data for the selection of welding mateial for welding of dissimilar steel of 25Cr35NiNbMA/20Cr32NiNb alloy steels is provided, and the welding process of dissimilar steel is optimized.