For the Q345R+904L stainless steel composite plate with 40 mm thickness,different welding materials are used to weld the base layer,transition layer and cover layer respectively. After welding,macroscopic inspection,metallographic analysis,mechanical property test,component analysis and intergranular corrosion test of welded joints are carried out according to relevant standards. The results show that the joints obtained by the welding scheme are well formed,the tensile bending and impact properties of the joints meet the standard requirements. The joints of the composite layer are welded by E309 LMo and E385 stainless steel welding consumables respectively. Both the weld zone and the heat affected zone have acceptable intergranular corrosion resistance.