On account of the traditional friction brake for heavy-duty truck (HDT), the massive quantity of heat accumulating constantly because of frequent using of friction brake system in the long and steep downhill road leads to brake temperature rising rapidly. Affected by structure frictional couple installed in the closed environment of the brake drum, it is difficult to dissipate the heat in time via heat conduction, heat radiation and heat convection, and the heat fade phenomenon of the brake emerges easily. The HDT would be in danger because of braking efficiency descending. This paper proposes an active water-cooled drum brake system (AWBS) to solve the problem. According to the principle of engineering thermodynamics, the structure and size of the back-stretching water jacket of brake shoe and the inner riveted the friction plate of brake drum are designed with restrained of GB 12676-2014 ‘Technical requirements and testing methods for commercial vehicle and trailer braking systems’. In order to meet the requirements of heat dissipation and structural strength for tractor and trailer, the composition and parameters of AWBS are proposed, including volume and type of coolant, radiator size, hydraulic pump parameters, tank capacity and connection type. To verify the performance of the system, the three-dimensional model and simulating model are established to simulate, the simulation results show that structure meet s strength requirements and the AWBS can significantly inhibit the rise of brake temperature, reduce the probability of brake thermal decay of heavy truck on long downhill, and improve the driving safety of the vehicle significantly.