This paper simulates a gas-assisted flow nozzle. First, establish a model of the nozzle, and select an appropriate calculation model according to actual working conditions. Liquid water and air at room temperature (25 ℃) are selected as the research medium. Using air pressure and hydraulic pressure as variables, the analysis of multi-parameter flow characteristics is studied, and the concept of gas-liquid ratio is introduced. After calculation, the static pressure, velocity and liquid phase distribution diagram inside the nozzle are obtained. The maximum pressure appears on the wall where the outlet part and the inlet part intersect. Due to the contraction inside the nozzle, negative pressure will be generated in the outlet part:the highest droplet inside the nozzle first appears at the nozzle,and then stabilizes at the intersection of the gas phase and the liquid phase; Finally, the largest droplet is produced at the nozzle. The liquid phase first fills the nozzle quickly and then gradually mixes with the gas phase. When the nozzle is sprayed, liquid water and air are evenly mixed. The influence of multiple parameters on the pressure, velocity and liquid phase distribution inside the nozzle is also obtained. The conclusion is that the Computational Fluid Dynamics method is used to obtain the internal state of the nozzle and the influence of multi-parameters on the flow characteristics, and to grasp certain laws, which provides help for further research and optimization of the nozzle structure and spray uniformity.