A numerical analysis model of thin-wall outer casing on aeroengine combustion chamber during laser welding is built. Weliding deformations due to circumferential weld of thin-wall outer casing on cunbustion chamer is studied by numerical analysis based on Sysweld. The temperature field, stress field distribution and welding deformation in thin-wall outer casing during laser wilding are simulated. The problem of heat source during welding simulation is analyzed and investigated mathematically.Then the analysis results are qualitatively discussed according to the factual working conditions of whole thin-wall outer shell for validating the feasibility of the analysis method.