Spray tests were conducted with a 3WQF120-12 fuel powered singlerotor UVA to study the distribution regularity of droplets deposition during aerial spraying with plant protection unmanned aerial vehicle (UAV) in cotton field.Imidacloprid and carbosulfan were separately sprayed with UAV under two spray dosages including conventional dose and 20% dose reduction,and two spray volumes including 12 L/hm2 and 15 L/hm2.Allura red was used as tracer to measure the pesticide spray distribution.The parameters of droplets were tested with droplets test card and analyzed with image processing software DepositScan.The results showed that spray volume had a great influence on the droplets deposition of imidacloprid on cotton.The droplet depositions of imidacloprid on cotton were 99.64 μg/cm2 and 128.04 μg/cm2 under the spray volumes of 12 L/hm2 and 15 L/hm2 with the spray dosage of 90 g/hm2.The droplet depositions of these two volume groups on cotton were 75.09 μg/cm2 and 101.32 μg/cm2 when the spray dosage was 72 g/hm2.Spray dosage had a great influence on the droplets deposition of carbosulfan on cotton.The droplet depositions were 613.92 μg/cm2 and 801.59 μg/cm2 under the spray volume of 12 L/hm2 when the spray dosages were 480 g/hm2 and 600 g/hm2.The droplet depositions of these two dosage groups on cotton were 620.17 μg/cm2 and 870.64 μg/cm2 under the spray volume of 15 L/hm2.The results of analyzing droplets distribution showed that droplets density on the underside of cotton leaves ranging from 0.8 cm-2 to 238.9 cm-2 were higher than that of upperside when the spray volume was 15 L/hm2.The droplets density of the spray volume of 12 L/hm2 were lower than that on the upperside and underside of cotton leaves ranging from 1.4 cm-2 to 65.9 cm-2 and from 1.1 cm-2 to 110.7cm-2,respectively.The droplets size of the two spray volumes on the upperside of cotton leaves were larger and ranged from 83 μm to 441 μm and from 113 μm to 418 μm.The droplets size on the underside of cotton leaves were smaller and ranged from 72 μm to 242 μm and from 102 μm to 252 μm.It will provide references for applying and extending UAV to prevent and control pest in the cotton field.