Abstract: Based on inherent strain method,3D Gaussian + double ellipsoid heat source model was used to predict laser hybrid welding deformation of 8 m side wall components of a high-speed train under different welding sequence and constraint modes. The results showed that deformation in the thickness direction of side walls was greatly affected by welding sequence,and it could be reduced by about 13% after optimizing the welding sequence. The welding constraints had obvious influence on the arc profile and arc chord width of the side wall components,but had little influence on the overall length. Compared with unconstrained condition,the maximum deformation in the thickness direction was reduced to 25%,and the maximum deformation in the width direction was reduced to 10%. The comparison between simulation results and test results showed that the heat source model selection of the side wall component under its process conditions was effective and reasonable,and the numerical simulation of the measurement points was in good agreement with the actual tests,with the absolute error less than 1 mm.