Laser Shock Processing (LSP) is an excellent surface strengthening technology and an effective method to effectively solve this technical problem. The published literature only reports the LSP research on the blade tenon of large engine, and there is no LSP research on the turbine disk mortise of small engine (helicopter engine) with complex and narrow spatial structure. This paper was carried out Oblique LSP research on the complex structure of key parts of new helicopter engine, and the following research results were obtained: The residual stress of simulation and experiment were analyzed by the least-squares method, the flat-topped order of laser beam was corrected, and the pressure distribution model that better matches the shock wave induced by the flat-top laser beam was constructed; Due to the thin thickness and poor stiffness of the turbine disk mortise, the residual stress of the turbine disk mortise was compared between the LSP finite element simulation and the experiment by using the treatment method of equal laser power density and variable pulse width. The results show that the results of turbine disk mortise experiment were close to those of finite element simulation. The treatment method of equal power density and small pulse width can ensure the effect of strengthening the surface and reduce strain of turbine disk mortise.