Abstract: In order to achieve the purpose of reducing pesticide application while increasing efficacy, adjuvant has become an essential part of pesticide application process. The application amount of adjuvant directly affects the pesticide utilization. In order to study the effects of adjuvant on volume median diameter (VMD) of spray droplet and relative span of droplet size, a laser diffraction system was used to investigate the spray droplet characteristics of different adjuvants with different hydraulic nozzles. Three different adjuvants were tested with 2 types of nozzles, IDK120-025 and LU120-015, under laboratory conditions. The 3 adjuvants used in the experiment were Italy, Jijian and Urea. Italy and Jijian are standard adjuvants. Urea is a kind of chemical nitrogen fertilizer, and when it is dissolved in water the liquid becomes cloudy. Generally it is applied to aerial spraying solution to increase droplet settlement. As Urea does not belong to the standard adjuvants, its effect on the atomization of the liquid is not yet clear, and solving this problem is also one of the experimental purposes of this experiment. Italy and Urea are powdery and Jijian is liquid form. IDK nozzle and LU nozzle are widely used in the spraying, and the nozzle size and spray angle are the same, but the spay chamber atomization structure is different. The internal structure design of the IDK nozzle utilizes the Venturi principle to mix the spray liquid with the air inside the nozzle to make the ejected droplets become small bubbles. Studies have shown that changes in the physical and chemical properties of the spray liquid system play a decisive role in the correlation between the liquid film length and droplet size. Because the difference in physical and chemical properties of tap water and distilled water may affect the particle size of droplets, the experiment also uses tap water and distilled water as the experimental control groups. The results show that the 3 adjuvants have a more significant effect on IDK120-025. However, the spray mist droplet uniformity of LU120-015 nozzle is better than IDK120-025 nozzle. When the concentration ratio of Jijian solution is 1:3000, the VMD of droplets sprayed by IDK nozzle can be increased by 20.43% compared to water at a pressure of 0.4 MPa, and the relative span of droplet size can be reduced by 1.74%. When the concentration ratio of Italy solution is 1:2000, the VMD of droplets sprayed by IDK nozzle can be increased by 11.10% compared to water at a pressure of 0.4 MPa, and the relative span of droplet size can be reduced by 8.86%. When the concentration ratio of Italy solution is 1:3000, the VMD of droplets sprayed by LU nozzle can be reduced by 5.99% compared to water at a pressure of 0.2 MPa, and the relative span of droplets size can be increased by 1.56%. When the concentration ratio of Urea solution is 1:2 000, the VMD of droplets sprayed by IDK nozzle can be increased by 16.92% compared to water at a pressure of 0.4 MPa, and the relative span of droplet size can be reduced by 6.92%. According to the ASABE S572.1 standard to evaluate the result of the experiment, the spray quality of IDK nozzle is focused on medium and coarse grades, the VMD of droplets is large and the difficulty of retention on wet leave surface is moderate, and the drift potential is at medium level. The spray quality of LU nozzle is focused on fine grade, the VMD of droplets is small and the retention ability on wet leave surface is good, but the drift potential is high. This experiment can provide foundation for the selection of adjuvants and nozzles in field pesticide application, and provide the data basis for further research on new nozzles and adjuvants.