In order to improve the serious problem of "collision" when the retarder is installed in the transmission system of a semi-trailer vehicle, and to improve the braking energy recovery rate during retarding conditions, a scheme of energy recovery type retarder installed in the hub on both sides of the front axle of semi-trailer was proposed. According to the regulation of retarder braking performance in GB/T 32692, the retarder parameters are matched, and the corresponding retarder control strategy is proposed. According to the quality requirements of the electric semitrailer train in the control strategy, the quality estimation algorithm was studied, and based on the particle swarm algorithm, the braking torque distribution at low braking intensity is studied. A joint simulation platform was built through Matlab/Simulink and TruckSim to simulate and verify the quality estimation algorithm, the economy of electric semitrailer trains and braking safety. The simulation results show that the quality estimation algorithm can accurately estimate the quality of electric semitrailer trains; The energy recovery retarder can meet the retardation requirements of electric semi-trailer vehicles, improve the braking energy recovery rate, and can effectively improve the "collision" problem of the electric semi-trailer train during slow braking. Related research provides new ideas for improving the braking energy recovery rate of electric semi-trailer vehicles during slow braking, and can improve the "collision" problem and improve braking safety.