Abstract: According to the application requirements of large flow mud pump truck and the characteristics of open hydraulic system and closed hydraulic system, the hydraulic system of large flow mud pump truck is designed, and the working principle and functions of main hydraulic components are described in detail. Based on the performance parameters of mud pump truck, the important hydraulic components are calculated and selected. Considering the requirements of working environment and closed hydraulic system heat dissipation in coal mine underground, three corresponding cooling measures are adopted to improve the heat dissipation effect of the system, which can be well adapted to underground application in coal mine.