Abstract: Influence of plasma actuators on the flow separation control of NACA 0015 airfoil was investigated in an open-circuit low-speed wind tunnel.Particle Image Velocimetry(PIV)technology was applied to visualize the modification of the flow structure over the airfoil by the plasma actuators.Lift and drag were measured by a five-component strain gauge balance to investigate the separation control effect of the actuator voltage and excitation frequency.The results show that the leading-edge plasma actuators are effective in controlling the flow separation over the airfoil at low wind speeds.The maximum lift coefficient and stall angle are increased by 11%and 6 deg respectively at the free-stream velocity of 20m/s.However,at a given flow state,there exists threshold values for both the actuator voltage and excitation frequency on the actuators.The threshold values are different with the changing attack angles.At the higher attack angles,the plasma actuator's authority must be increased due to the much stronger flow separation on the airfoil.