Abstract: In order to solve the problems such as poor deposition effect of fog drops on the lower and middle layers of maize crops, low coverage rate of fog drops due to uneven distribution of fog drops in different canopy layers, poor pesticide spraying method and environmental pollution, a corn field spraying device was designed. The key parameters were determined by using mathematical theoretical geometric relations and Fluent software. the length of the boom was 1 950 mm, the height of the side under sprinkler head from the bottom of the boom was 50 mm, the height of the side above sprinkler head from the top of the plant was 50 mm, the angle between the side under sprinkler head and the horizontal direction was 38.8°, and the angle between the side above sprinkler head and the horizontal direction was 43.7°. Using Design-Expert software, a three-factor and three-level orthogonal test was designed with the pressure at the upper nozzle of the boom side, the pressure at the lower nozzle of the boom side and the traveling speed of the machine as the test factors, and the average fog drop coverage rate of the blade Y as the test index. According to variance analysis, the primary and secondary order of factors affecting fog drop coverage is: moving speed ＞lateral lower pressure ＞lateral upper pressure. After field test, the final combination parameters are as follows: the machine speed is 0.8 m/s, the lateral upper pressure is 0.7 MPa, the lateral lower pressure is 0.5 MPa, and the fog drop coverage rate is 26.54%,The fog drop coverage rate of upper, middle and lower leaves was 28.32%, 23.54% and 27.75%, respectively, and the relative error between model simulation and field test was 5.05%.The research results can provide reference forthe development of corn plant protection machinery.