Due to the small distance between the inlet port and the propeller blade, the propeller slipstream has a great impact on inlet flow field. In order to study this impact, unsteady CFD Methods are used to simulate inlet aerodynamic performance under the influence of propeller slipstream. The results show that: in the state of on ground and takeoff, the exit total pressure recovery coefficient is higher with slipstream than without it while the exit total pressure recovery coefficient is lower with slipstream in cruise flight. The primary factors cause the difference lie in whether propeller in front of the inlet does work to the airflow. Besides,when the flow from side channel flow backwards into inlet, the propeller slipstream will increase the distortion factor of the flow at the exit. The reason is that the slipstream will cause perturbation to the inlet flow field as propellers sweep past the inlet periodically. Also, the propeller wake will flows into inlet periodically. Thus, both of the two reasons will reduce the uniformity of the flow field in the inlet.