To make full use of engine exhaust heat and further improve the utilization of the energy efficiency of the heavy truck, thermoelectric module is used to contribute to thermoelectric power generation. The hot-end temperature of the module varies with the engine operating condition because it is connected with the exhaust pipe. The cold-end of the thermoelectric module is mainly cooled by engine cooling system. Increasing the temperature difference between the hot-end and cold-end of the thermoelectric module is a good way to improve the thermoelectric conversion efficiency. For the poor controllability of the hot-end temperature of the thermoelectric module, this study puts forward by lowering the cold-end temperature of the thermoelectric module so as to ensure the improvement of the thermoelectric conversion efficiency. The cooling circle for the cold-end of the thermoelectric module which is independent of the engine cooling system is built. The nucleate boiling flow is adopted to strengthen the heat transfer from the thermoelectric module cold side to the cooling water. The boiling temperature of the cooling water is reduced by setting the vacuum degree of the cooling system so that the phase transition occurs in the reasonable temperature range and the heat removal capacity from the cold-end of the thermoelectric module could be enhanced. Consequently, the cold side of the thermoelectric module is decreased and the temperature stability could be effectively achieved..