Abstract: With the heavy-load planetary gear made of 20CrMoH steel as the research object, and was verified a multi-field coupled carburizing and quenching finite element model was established by using the Abaqus finite element software and its secondary development functions. The residual stress, hardness, carbon content, phase composition and deformation amount distribution of the gears in carburizing and quenching (carbon potential of 1%, carburizing temperature of 880 ℃, quenching oil temperature of 110 ℃) was predicted and analyzed. The results show that the relative errors of residual stress and hardness simulation with the test results of the gear after carbonizing quenching were all within 10%, proving that the established multi-field coupled carbonizing and quenching finite element model was reliable. The axial stress on the surface of the gear was residual tensile stress, approximately 430 MPa, and that of the core part was residual compressive stress, approximately 126 MPa. The carbon content of the gear gradually decreased from the surface to the core, and the depth of the carbonizing layer was approximately 1.1 mm. The martensite content from surface to core in the gear was the highest, and the volume fraction of martensite on the surface was close to 100%. During the carbonizing and quenching process, the deformation amounts in the x, y, and z directions of the gear tended to be consistent. The deformation amount reached the maximum when the gear was completely austenitized and the temperature reached 880 ℃, which were approximately 0.239, 0.025, 0.206 mm in x, y, z directions. After carbonizing and quenching was completed, the deformation amounts in x, y, z directions were approximately 0.117, 0.017, 0.089 mm.