In order to study the effect of droplet size spraying by unmanned aerial vehicle(UAV) on droplet deposition in rice canopy, the distribution of deposition of four different volume median diameter(VMD) droplets in rice canopy was analyzed by using colorimetric method. The experiment used xylidine ponceau 2R as tracer, and the equation of linear relationship between the mass concentration(x) and absorbance value(y) of xylidine ponceau 2R was follows: y=0.095 1x– 0.012 9. We tested 4 kinds of spray droplets’ sedimentary distribution results, whose VMD is 218 μm, 200 μm, 178 μm and 145 μm, in upper, middle, lower of rice plants. The significance of droplet deposition data was analyzed by SPSS software, the results was that the Sig. value of factor of vertical sampling position was 0.032 and the Sig. value of factor of experimental co mmunity was 0.000. The results showed that droplet deposition existed significant differences between upper, middle and lower in rice canopy, and the deposition volume in lower was even more than that in upper and middle. Droplet deposition in different experimental plots also existed significant differences, which means that the spraying droplet size has significant effect on droplets depostion on target. About four experiments, the mean liquid deposition volume increased with the decrease of droplet size in sampling points. Among them, the plot A’s deposition volume was 0.52 μL/cm2, which was the minimum. Plot D’s deposition volume was 0.99 μL/cm2, which was the maximum. In addition, for 4 experiments, the variance coefficient of plot D’s deposition volume were relatively lower, which were 8.40%, 17.86%, 14.92%, and the the variance coefficient of plot A’s deposition volume were relatively higher, which were 33.86%, 32.04%, 34.06%. Above results indicated that spraying droplets’ distributed uniformity and penetration were good in the test, and the smaller the droplet size , the more the deposition volume per unit area and the better the distribution uniformity. Under the action of wind field produced by UAV’s rotors, because the droplets can effectively penetrate the canopy and reach the depths of the canopy with the action of the wind field formed by UAV’s rotors. This test got the relationship between spray droplet size and droplet deposition within a certain size range, and analysed droplets’ penetration of spraying by UAV, which could provide a certain reference for droplets parameter setting when spray by UAV and have a certain guiding significance to improve the spraying efficiency and reduce pesticide use.