Abstract: The VOLVOEC75D small excavator adopts a load sensing control system. The hydraulic system has the characteristics of high productivity, strong digging ability, high control accuracy and fuel economy. This article introduces the structure and control principle of the main pump of the VOLVOEC75D small excavator, analyzes the common faults and troubleshooting methods of the main pump of the EC75D excavator, and introduces the power of the main pump and the method of adjusting the pressure difference of the pump in detail, in order to correctly grasp the The maintenance and adjustment of the pump play a certain guiding role.