The transient and then residual stress in welded joints with thermal expansion coefficient (simply TEC) mis-matching between the weld metal and the parent metal are investigated by using the method of thermal elasto-plastic finite element analysis in this paper. Results of the computation under the same welding heat source show that, longitudinal residual stress σx located in the weld center changes with the yield stress σs of the parent metal under the TEC even matched joints, the residual stress σx is close to equal to the stress σ when the stress σis low,and is abviously lower than the stress σ when the stress σ is high. Besides, the stress σx is lower than the stress σ and drops with the TEC of the weld metal decreasing, and the residual tensile stress σx possibly transverses into the compressive in the TEC undermatched joints. However,the stress σx in the weld center also changes with the strain hardening exponent Hs of the weld metal in the TEC over matched joints. The residual stress σx in the weld center attained as high as σ increases little when Hw' is low,but is somewhat higher than σwhen Hw' is high. The above conclusions are important to design or elect weld e1ectrodes.