Abstract: The complex unsteady aerodynamic problems and slipstream caused by the non-axial yaw inflow of a four-blade propeller during flight were studied using numerical simulation. By combining the unsteady Reynolds-averaged Navier-Stokes equation with the slip mesh method and using the yaw angle, incoming flow angle of attack, and inflow velocity as variables, the characteristics of the propeller such as unsteady thrust force, moment and propulsion efficiency, as well as the slipstream field distribution under different working conditions, were obtained. The results show that when keeping the angle of attack and the incoming flow constant, raising the yaw angle from 15° to 25° leads to an increase in the propeller pulling force and propulsion efficiency by 16.20% and 6.76%, respectively. There is a positive correlation between the aerodynamic characteristics of the propeller and yaw angle change within certain limits. Yaw inflow leads to a certain degree of deflection in the slip flow field distribution behind the propeller and the tip vortex. As a result, the propeller wake shortens and the wind velocity in the slipstream area recovers. Furthermore, the unsteady aerodynamic characteristic coefficient of the propeller increases as the angle of attack rises. The propeller aerodynamic performance is consistent in both yaw inflow coupling low angles of attack and the high angles of attack flow without a yaw angle. Also, the strengths of the four propeller tip vortices are not equal, exhibiting asymmetry. Thus, yaw inflow has a significant positive effect on the aerodynamic performance of the propeller.