Abstract: GTAW technology has been used to fabricate welded connections on composite plates consisting of 304 and Q355 materials. Base material thickness was 13 mm, while cladding material thicknesses ranged from 0.3 mm to 2.0 mm. The influence of different thicknesses of cladding material on the stress and strain of 304/Q355 composite plate welded joint was analyzed by numerical simulation method, and the evolution characteristics of residual stress and strain during welding of stainless steel composite plate with different thicknesses of cladding material were revealed. The results show that the X-ray diffraction test results are in good agreement with the numerical simulation results. With the increase of the thickness of the cladding material, the maximum residual stress value of the welded joint section of 304/Q355 composite plate gradually decreases, and the width of the residual stress zone gradually increases. During the welding process from the base weld to the transition weld, the stress concentration zone gradually shrinks to the transition weld zone. Finally, the highest stress concentration area is located in the weld zone of the transition layer, and the maximum stress value is close to the yield strength of the material. In addition, the deformation after welding increases with the increase of the thickness of the cladding material, and the deformation of the composite plate with the thickness of the cladding material 2.0 mm is about 2 mm higher than that of the composite plate with the thickness of the cladding material 0.3 mm, and the direction of the largest deformation is the direction of the weld thickness.