Abstract: Elasto-plastic finite element method is used for simulating the welding temperature field and the residual stress in butt-welded Q235 and 304 stainless steel.The results indicate that differences between their physics property caused the inhomogeneous distribution of the welding temperature field and the residual stress.And the peaks of the residual stress show on 304 stainless steel side,and the peak value is slightly less than the yield strength of 304 stainless steel.When the heat source was moved towards Q235,the peak value had small changes,but the high-stress and the welding distortion were decreased.On the contrary,when the heat source was moved towards 304 stainless steel,the high-stress area would be expanded with higher welding heat,and the peak value of the residual stress was slightly decreased.An infrared thermal imager was also applied to measure surface temperature changing of welding materials in welding process,the results are in accordant with that drawn from elastoplastic finite element simulation.