Abstract: Very high cycle fatigue tests were carried out on the axial high-frequency fatigue testing machine. The fatigue characteristics of carburized gear steel under different stress ratios (R=0 and R=0.3) were studied. The results show that when the stress ratio is 0 and 0.3, the failure modes of carburized gear steel are divided into surface failure and interior failure. The interior failure process is divided into fatigue crack initiation stage (from inclusion to fine granular area (FGA)), stable propagation stage (from FGA to fisheye) and instantaneous fracture (outside fisheye). Based on the cumulative damage method, the life prediction models of interior crack initiation and propagation stages are established, respectively. Finally, the fatigue life prediction model of carburized gear steel is established, prediction accuracy is higher.