The quantitative pump electro-hydraulic load sensing system was designed for the working device of hydraulic rotary tiller. Compared with traditional constant flow load sensing system, the combination of permanent magnet synchronous motor and quantitative pump was used to replace the three-way pressure compensation valve. The schematic diagram of hydraulic system and the control block diagram of the system were given, and the mathematical model was built to analyze its control strategy. The system simulation model was built through AMESim to simulate and analyze the power curves and energy curves of each actuator of the rotary tiller working device to work alone and compound action, so as to analyze the energy consumption of the system. The results show that the system dynamically adjusts the output flow of the quantitative pump through the permanent magnet synchronous motor; the output power of the quantitative pump changes with the load, so as to reduce the overflow loss of the system, increase the energy utilization rate of the working device of the rotary tiller, and improve the energy-saving effect of the system.