Abstract: Abstract: In order to find out the factors and degree of influence affecting small unmanned helicopter spray deposition, and formulate the corresponding test methods and specifications through experimental results, this paper studied the relationship between spray deposition characteristics and flight height, flight velocity of an unmanned helicopter and the interaction between two factors, and arranged a test by a second factor three level test. An experiment was conducted with a diameter of 90 mm glass sample dish as collecting droplets sampling tools, setting up six sampling points, with the interval of sampling being 5 m, and each sample dish was placed on the top of wheat, about 0.8 m. Then 10 mL of distilled water was added in the sample plate in advance as a sample base to collect settlement droplets in the spray test. A 4 g/L carmine solution was selected as medium for spraying, monitored wind speed of flight direction refer to meteorological station monitoring method in spraying test, at the same time, monitored humidity and temperature. Then t the collected samples were measured by UV-2102 PCS type ultraviolet visible spectrophotometer, first, scan absorption wavelength of carmine solution, selecting = 508 nm as the measurement wavelength to measure absorbance. Secondly, a carmine standard solution was prepared in 0, 0.025, 0.05, 0.075 and 0.1 g/L to establish a mathematical model of concentration and absorbance and convert concentration into absorbance under the established wavelength, and convert taken samples measurement results into concentration according to the mathematical model. Finally, absorbance of taken samples were converted into mass concentration, that is a quality of carmine per square centimeter as the experimental results for data analysis. Next, the significance level α = 0.05 was selected. The average concentration and the coefficient of variation to variance and regression analysis was selected to study the degree of effect of unmanned helicopter flight velocity, flight height, and interaction of these two factors to deposition concentration and deposition uniform. The analysis results showed that: flight height, flight velocity of unmanned helicopter, and the interaction between these two factors have a very significant impact on the deposition concentration, the respective P-value values is 2.0684×10-4, 8.2190×10-,5 and 9.7052×10-5; flight height, flight velocity of an unmanned helicopter has a very significant impact on the deposition uniformity, the respective P-value values are 9.8410×10-3 and 1.1550×10-3; the interaction between the two factors have a significant impact on the deposition uniformity, and the P-value values are 2.5594×10-2. The model established respectively between deposition concentration, deposition uniformity and flight height, flight velocity, in interval range of the flight velocity and flight height was not significant, and the respective regression equation lost to test is FLf=3.7024