It is difficult for the chemical spray droplets to deposit on rice leaves. Thus, deposition area of chemical droplets on rice leaves was researched. Firstly, by using scanning electron microscopy (SEM) method, the microstructure of both sides of two varieties rice leaf was observed in different growing stage(tillering stage and booting stage). And the mastoid diameter was 1.5~4.2 μm, while the length of hook hair was 70.4~154.5 μm. There was large difference in microstructure and more mastoid was in per unit area. Then, based on the rice leaf wetness theory, the calculation methods for fall-off critical droplet diameter were deduced. According to fall-off diameter size pesticide droplets on rice leaves in different surface microstructure, it deduced that the main deposited parts was the glochuid of silification-cork belt. Finally, rice leaf sprayed with talcum powder suspending liquid and SEM method was used to verify the pesticides deposition part. 