Abstract: The temperature of gear systems was measured with a closed power flow gear test rig. It is the first time that the temperature fields of gear systems were solved by combining finite element method and thermal elastohydrodynamic lubrication method. To get the convection heat transfer coefficient accurately, the viscosity-pressure-temperature equation and the density-pressure-temperature equation were introduced to finite element analysis. The highest temperature and flash temperature of each point in the meshing line and their distribution laws along the line of action were obtained with the bulk temperature solved with finite element method as the initial temperature of the thermal elastohydrodynamic lubrication calculation. The results show that the bulk temperature solved with finite element method is consistent with the test results. The flash temperature distribution calculated with thermal elastohydrodynamic lubrication method is close to the ISO flash temperature. With increasing modification coefficient, the highest bulk temperature area transfers from the dedendum to the addendum.