The process of heat transfer in tracked vehicle transmission was investigated. A heat transfer model based on lumped parameter method has been developed in order to study heat transfer within the tracked vehicle transmission. And a flow model was established to predict oil flow in transmission fluid system by using 1-D incompressible flow theory. The whole heat transfer simulation model was completed based on the coupling of 1-D flow model to lumped thermal method. The program was carried out, which was used to calculate the heat transfer process under different operating conditions, and simulation results were compared to the test data with good agreement. The solutions are of great value in analyzing the heat transfer for tracked vehicle transmission.