Being a new type of active flow control technology, the plasma flow control can significantly improve the aerodynamic performance of aircraft. In this paper, the flow separation control of a UAV is studied by nanosecond plasma aerodynamic excitation. The experimental results show that the nanosecond discharge and the millisecond discharge are almost equal in excitation voltage, but the current generated by nanosecond discharge (30 A) is much larger than that generated by millisecond discharge (0.1 A). The induced effect of nanosecond plasma is similar to an upward shock wave produced in the flow field, and the maximum induced velocity is less than 0.5 m/s. The rapid temperature rise effect of nanosecond discharge induces a shock wave in the still air. The shock wave lasts about 80 microns and travels at a speed of about 380 m/s. Withthe nanosecond plasma aerodynamic excitation being used, when the excitation voltage is greater than a certain threshold value, the flow separation on the suction surface of the UAV can be suppressed. The critical stall Angle of attack can be increased from 20° to 27°, and its maximum lift coefficient increases by 11.24%. Furthermore, the optimal excitation frequency of nanosecond plasma aerodynamic excitation is the value to make the dimensionless numbers 1. In the boundary layer flow control, the nanosecond plasma aerodynamic excitation is more effective than the millisecond plasma aerodynamic excitation. The main mechanism of nanosecond plasma flow control is impact effect. The impact effect is more effective than the dynamic effect in highspeed flow control.