Abstract: With the increase in engine horsepower and average speed of heavy-duty commercial vehicles, hydraulic retarders account for >80% of long-distance transportation tractors.At present, the match of the hydraulic retarder is according to the fitness of braking ability.Based on the three dimensions of auxiliary braking performance, economy and noise, the matching control of hydraulic retarder is carried out, and the noise and economy of the vehicle can be improved on the basis of ensuring the braking performance of the hydraulic retarder by matching the appropriate speed ratio and optimizing the downshift speed of the retarder and the fan speed.