The hydraulic retarder is a significant auxiliary braking device  for the heavy duty vehicle. Traditionally, cooling circulatory system of the hydraulic retarder was coupled with the engine cooling system , and the thermal energy of the transmission medium would be cooled by the engine radiator ultimately. For this scheme, radiator's spare heat removal capacity could be fully utilized whereas the cooling system is very complicated and is hard to maintain. Furthermore, the corresponding of thermal management system lags behind the power change of the retarder.In this research, integrated cooling evaporation system is developed for the hydraulic retarder, which makes the cooling water contact with the transmission medium through the stator wall, so that it can rapidly response to the thermal variation of the retarder, keep the stability of the oil temperature and meanwhile reduce the risk of cooling medium leakage.First of all, transmission medium flow regime in the retarder is established for the specific driving condition and the transmission medium flow rate under different gyration radius is analyzed. Then, the integrated cooling evaporation system is designed and its heat transfer model is built in order to analyze the temperature stability of the transmission medium and flow characteristics of the cooling medium under different working conditions.The results show that, compared to the traditional plate-fin heat exchanger [3,4,5,6], the heat-sinking capacity increases 100% to 200% and the transmission medium temperature is in the optimal operating temperature range of 80°C to 120°C. As a result, the real-time control of the thermal management system is better. All of this contributes to the enhancement of the stability and durability of the hydraulic retarder.