Considering the influence of heat treatment process on the contact fatigue life of carburized Cr-Ni gears, the contact fatigue life prediction model of carburized gears is constructed. The gear contact fatigue test is carried out by using the gear contact fatigue test machine, and the gear contact stress is calculated based on Hertz theory. The S-N curve is drawn according to the test results. Through the observation of tooth surface morphology and the comparison with the test data, it can be seen that the contact fatigue life of the gear before the pitting phenomenon is formed accounts for the main part, and the gear will fail rapidly after the pitting phenomenon occurs. Based on Paris formula, considering the local and overall hardness, residual stress, crack closure effect and crack length of gear, the contact fatigue life prediction model of gear is constructed. The model prediction results show that the model can accurately predict the gear contact fatigue life, which provides a new and reliable method for people to understand the gear contact fatigue characteristics and predict the gear contact fatigue life.