Abstract: The carburizing and quenching process of 20CrMnTi thin-walled gears used in actual working conditions was simulated by finite element software Deform. The results show that after carburizing and quenching of thin-walled gears, the thickness of the carburized layer is 1.2 mm, and the quenching structure is mainly composed of martensite and retained austenite, and the retained austenite on the surface is 4.2% more than that of the core. The non-uniform temperature field and the structural stress lead to 9% deformation in the radial direction.The residual stresses on the surface and core of the gear are calculated to be-256.5 MPa and 141 MPa, respectively. The actual measurement results show that the thickness of the carburized layer of the thin-walled gear is 1.15 mm, the surface structure of the gear after quenching is composed of acicular martensite and 7% retained austenite and granular carbide, and the core structure is composed of low carbon martensite and 1% retained austenite, the residual stress on the gear surface is(-1078±168.2) MPa, and the maximum radial deformation is about 7%, which corresponds well to the simulation results. In order to solve the deformation caused by excessive internal stress under the comprehensive action of thermal stress and microstructure stress in the heat treatment process of thin-walled gear, cooling in different parts at the same time or radial restraint measures are adopted.