In the working process of hydraulic retarder, idle power loss will occur under non-braking condition. In order to reduce the air loss, three-dimensional flow field numerical simulation was carried out for the air loss of the spoiler mechanism with and without installation at different speeds. The pressure field and velocity field of flow field are analyzed, and the suppression effect of spoiler mechanism on air loss is analyzed. Taking the structural parameters of the turbulence mechanism as design variables, the parameters of the turbulence mechanism were optimized. The RSM model was built through DOE test design, and the structural parameters of the optimal turbulence column were obtained by the second generation of non-inferior sequencing genetic algorithm. Compared with the loss reduction rate before and after optimization, the average loss reduction rate of the optimized turbulence mechanism can reach 9.5%.