According to the motion characteristics of anti-drag braking of hydraulically driven vehicles, the influence of hydraulic pump displacement on the downhill braking performance of hydraulically driven vehicles is analyzed, and the principle of reasonably exerting the downhill anti-drag braking ability of hydraulic system and engine is proposed, and experimental verification is carried out. The results show that the size of the displacement of the hydraulic pump directly affects the braking performance and volumetric efficiency of the hydraulic system, and also determines the size of the engine anti-drag braking ability, the braking energy distribution relationship between the hydraulic system and the engine, and affects the change of motor speed.