Laser cladding welding of 1Cr17Ni2 martensitic stainless steel sheet on 27SiMn alloy structural steel was carried out under different welding conditions by laser welding. The laser welding simulation was carried out under the same conditions by Msc.Marc software. The finite element numerical simulation results are compared with the experimental data.The compar-ison results show that the Marc finite element software can effectively predict the welding stress and strain,and can pretreat the material according to the simulation results to reduce the residual stress. Under the condition that the laser power is 400 W and the welding speed is 0.8 m/min,the rigid displacement of the plates is constrained by the fixture in the experiment and simulation,and the deformation of the welders is reduced by 95.3% and 95.9% respectively. At the same time,the welding deformation was simulated and corrected by the prestress method. Under the tension of 800 N,the plate deformation was reduced by 29.3%. The test results show that the method of rigid fixation and prestress can effectively reduce the welding deformation.