Abstract: A thermal equilibrium analysis model for high-speed and heavy-load gear systems in time domain was established. The temperature rise formula of tooth surface was deduced and the rules of temperature varied over time at contact point as well as flash temperature distribution along action line were studied with numerical method. A thermal elastohydrodynamic lubrication (TEHL) analysis model which was more appropriate for actual conditions was proposed. In this model, the bulk temperature was chosen as the initial temperature and the maximum temperature rise of contact point were the flash temperature of contact point. The flash temperature and film thickness ratio distribution along action line were obtained. Blok theory and TEHL theory were comprehensively analyzed at last. The results show that the flash temperature solved with two numerical methods in this paper is very close to Blok flash temperature; and the TEHL theory is closer to the actual situation in theory. The results solved by TEHL theory could provide flash temperature and film thickness as well as other parameters to design and check the scuffing load capacity.