Abstract: To study the influence of incoming flow and crosswinds on airflow field of a single rotor plant protection UAV, we used a Wall-Adapting Local Eddy（WALE） model based on lattice Boltzmann method to simulate the airflow field of Copterworks AF25 B single rotor oil-powered plant protection UAV. we set Different forward flow and crosswinds velocity and numerical simulation were set to research the effects of different incoming flow and crosswinds velocity on the airflow field of a single rotor plant protection UAV. The results show that the direction of forward incoming flow is opposite to the direction of the wake of the front vortex. When the forward flight altitude of the UAV is constant, the forward flight speed increases from 3 m/s to 7 m/s, and the inclination angle of the airflow field increases by 116.67%, reaching 71°, and secondary offset occurs. The velocity of the airflow field follows an “M” shape structure. At a certain forward flight height, the distance between the peak velocity on both sides of the airflow field narrows with the increase of the forward flight speed, while the location of the peak velocity and the distance between the rotor axis increases. At a constant forward flight height and speed, the airflow field of the single-rotor plant protection UAV deflects at different angles with the increase of crosswind, and the angle is proportional to the crosswind speed. The flow structure in the airflow field is similar to that in the absence of crosswinds, showing a “U” shaped structure. Under the same forward flight height and speed, the x-axis offset of the airflow field at different crosswinds obeys the second-order law. This study lays the foundation for further study on the basic characteristics of fog droplets by airflow field and guides the planning of spraying path operation.