Abstract: In order to determine the effect of current mainstream plant protection UAV operation parameters on the distribution pattern of droplet deposition in tobacco fields at different stages, and obtain the optimal distribution effect of droplets, an electric multi-rotor plant protection UAV was adopted and a three factor and three level orthogonal experiment was conducted to optimize the combination of three operation parameters, i.e. flight height, flight speed, and pesticide application amount. And the effective spraying range of plant protection UAV in tobacco field was tested. The results show as the followings. (1) The optimal operation parameters in root extension stage are flight height of 3 meters, speed of 4 m/s, and liquid application rate of 15 L/ha. (2) The optimal operation parameters in fast growth stage are flight height of 3 meters, speed of 5 m/s, and liquid application rate of 15 L/ha. (3) The optimal operation parameters in maturity stage are flight height of 5 m, speed of 4 m/s, and liquid application rate of 30 L/ha. (4) The spraying range for plant protection UAV operation on tobacco should be 3-4 m. The results can provide a theoretical basis for plant protection UAV applied in pest control at different growth stages of tobacco.