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The use of aircrafts is becoming increasingly common in carrying out this task mainly because of their speed and effectiveness in the spraying operation, but most of the spraying research with UAVs is still in its initial stages.In this paper, we describe the droplet distribution of unmanned aerial vehicle (UAV) spraying for citrus canopy at the first time, and evaluate the spraying effect in various conditions.Moreover, we evaluate the impact of the different heights and nozzles.The 10-year-old HongJiang orange (Citrus sinensis(L.) Osbeck,"Hongjiangcheng") grafted on Trafoliata (Poncirus trifoliata (L.) Raf.) was selected as experimental material in this experiment.A four-rotor UAV was employed to test the UAV spraying effects.Ponceau 2R was selected as the chromogenic agent, formulated 300 times solution as the experimental reagent, paper cards were clipped in the different parts of the canopy to collect the droplets.Droplets deposition parameters were extracted and analyzed using digital image processing.The results indicated that, 1) Droplets deposition in upper of the canopies was more than that at the middle and bottom of the canopies.The average droplet coverage in upper, middle and lower is 10.70 deposits/cm2, 6.59 deposits/cm2,and 4.35 deposits/cm2, respectively.In the flight direction of UAV, droplet deposition in the right of canopy was better than that in the left and middle, the right side of canopy also has smaller particle size, 0.64mm;and there were no significant difference of droplet deposition between canopies in the front, middle and rear parts.2) The droplet deposition was affected by the UAV flying height.On the whole, droplet coverage ,the total number of deposition and deposition densities at the target leaves reached maximum when the working height was 1meters, they were 7.75%, 2550, 25 per square centimeter, respectively.These parameters compared with working height of 2 m have increased by 15.50%, 21.37% and 19.05%, compared with 0.5 m, these parameters increased by 85.85%, 248.84% and 257.14% respectively.With the increasing or decreasing of the working height, the droplet deposition declined.3) The droplet diameter of rotating centrifugal nozzle(0.26mm) is apparently less than that of pressure nozzle(0.53mm).Whereas the total amount and density of droplet deposition of rotating centrifugal nozzle are better than the pressure nozzle.The best droplet distribution using UAV spraying was acquired in upper canopies, and the UAV spraying performance was relatively stable.The droplet distribution is achieved when working height is 1.0m above the canopy.Compared to the pressure nozzle, the use of rotating centrifugal nozzle could significantly reduce the waste of chemicals.