Abstract: Aim at the difference between ISO 6336 and AGMA 925 standards on the calculation methods of gear surface damage such as scuffing, wear, micro-pitting and so on, this paper studies the difference of contact temperature and specific lubricant film thickness ratio in detail. The standard on the capacity of gear surface damages is studied from three aspects, including principle analysis, theoretical calculation and experimental cases. The calculation of multiple examples is conducted to compare the contact temperature, lubricant film thickness and safety factors of the gear surface under two different standards. The research results indicate that there are differences in the calculation methods of gear surface load in ISO 6336 and AGMA 925 standards, and differences in the fitting of the friction coefficients, resulting in differences in the calculation results. AGMA 925 uses the bulk temperature to calculate the local lubricant viscosity, while ISO 6336-22 uses the local sliding coefficient to consider the impact of the flash temperature on the local lubricant temperature. Therefore, the oil film thickness calculated by ISO 6336-22 is lower than that by AGMA 925 standard at high flash temperature points. Due to the different risk assessment results calculated by different standards, each standard result should be compared during the design process to improve the accuracy of risk prediction.