Abstract: In order to reduce the pollution of pesticides to the environment and achieve precise fertilization, an efficient, precise and simple electronically controlled precise spraying system is designed and applied to the trailed sprayer. Based on the PLC controller, a closed-loop control system consisting of data setting, data transmission, flow control, data acquisition, upload calculation, and comparative analysis is established. PLC outputs control signal to control the opening of electromagnetic proportional valve and electromagnetic pressure regulating valve to realize system flow and pressure regulation. The field test of the prototype machine takes the walking speed of the traction sprayer, the system pressure, and the set spraying rate per unit area as the test factors, and the deviation between the spraying rate per unit area and the set value and the coefficient of variation of the maximum spray rate of the nozzle are used as the test indicators. Orthogonal test to determine the optimal combination of test parameters. The test results show that when the walking speed of the traction sprayer is 7km/h, the normal working pressure of the system is 1.0MPa, and the spraying rate per unit area is 50L/mu, the deviation between the spraying rate per unit area and the set value is less than 3%, and the spray head The maximum spray volume coefficient of variation is less than 10%. The results show that the system has good stability and precise controllability. It meets the requirements of market use, conforms to national inspection standards, and has social promotion.