Rolling contact fatigue(RCF)properties of SAE 8620 steel after case carburizing have been investigated under two contact stresses of 4.0and 5.5GPa.Results show that the RCF life ranges from 2.5×10~6 to 3×10~7 cycles under the contact stress of 5.5GPa,while it can be more than 1×10~8 cycles under the contact stress of 4.0GPa.The rated fatigue life L_(10)(lives with the 10%failure)is also drastically shortened from 9.8×10~6 to 5.4×10~5 cycles when the contact stress is increased from 4.0to 5.5GPa.Theoretical calculations and fractographs show that the maximum shear stress and the contact area increase with increasing the contact stress,making RCF tend to occur earlier. Rolling contact fatigue (RCF) properties of SAE 8620 steel after case carburizing have been investigated under two stresses of 4.0 and 5.5 GPa. Results show that the RCF life ranges from 2.5 × 10 ~ 6 to 3 × 10 ~ 7 cycles under the contact stress of 5.5 GPa, while it can be more than 1 × 10 ~ 8 cycles under the contact stress of 4.0 GPa. The rated fatigue life L_ (10) lives with the 10% failure is also drastically shortened from 9.8 × 10 ~ 6 to 5.4 × 10 ~ 5 cycles when the contact stress is increased from 4.0to 5.5GPa. Theoretical calculations and fractographs show that the maximum shear stress and the contact area increase with increasing contact stress, making RCF tend to occur earlier.