Abstract: In order to study the operation effect of plant protection UAV in maize pest control and foliar fertilizer spraying, the orthogonal test was carried out by taking the flight height and flight speed of UAV as the test factors,and the droplet deposition density and droplet deposition uniformity of maize at the upper, middle and lower levels of plant protection UAV under different operating parameters were analyzed, and reasonable operating parameters were selected by combining range and ANOVA. The test results show that when the flight height of UAV is 2.5 m and the flight speed is 5 m/s, the effect of UAV application is better, the droplet deposition density of the upper, middle and lower layers is 10.89, 4.18 and 2.65 pcs/cm~2, respectively, and the uniformity of droplet deposition is 25.06%, 27.4% and 48.56%, respectively. At the same time, considering that the operating altitude of the UAV is limited by the operation location, the optimal flight speed parameters of the UAV at different flight altitudes are: height 2m and speed 5 m/s; height 2.5 m, speed 5 m/s; height 3 m, speed 5 m/s.