A droplet deposition and drift distribution model was established for super-high clearance boom sprayer with air-assisted system in accordance with the actual structure of sprayer. The CFD software ANSYS Fluent was used. The standard k-ε turbulence model, discrete phase model and couple algorithm were adopted. The simulation test was designed to study the relationship of drift rate with its influencing factors. The functional relation of droplet drift rate with its influencing factors at different rotation speed of axial-flow fan was established and the accuracy of the simulation result was validated. The results showed that, the model was well fitted, and the parameters of air-assisted system can affect the drift significantly. These conditions include angle of air-assisted flow, nozzle horizontal position, natural wind velocity, rotation speed of axial-flow fan, interaction between angle of air-assisted flow and natural wind velocity, interaction between angle of air-assisted flow and rotation speed of axial-flow fan, interaction between nozzle horizontal position and natural wind velocity, interaction between rotation speed of axial-flow fan and natural wind velocity. 