A coupled method based on numerical computation of heat transfer and experimental analysis was presented to estimate thermal loads on seals of the transmission. According to the working conditions of sealing rings, the transfer rule in the sealing system was investigated. Then the method to calculate the frictional heating of seal end face was put forward. Selecting reasonably boundary conditions on seal and simulating the actual operations of transmission, thermal responses such as temperature field and distribution, thermal deformation, and their variable curves between pressure and rotating speed were obtained by numerical computation of heat transfer. An experimental investigation was performed in the dynamic sealing performance test rig, by comparison of numerical and experimental results to enable an assessment of the accuracy level. Experimental results indicated that the predicted data agree well with test data. This estimation method can accord with the actual working mode, and has excellent reliability to predict sealing performances under thermal loads. 