Abstract: A new type of splayed-slit-synthetic-jet-actuator(SSSJA)which is useful for sepa-ration flow control was designed.The core component of the acoustic excitation type actuator was a powerful loudspeaker(4 W).The j et velocity depends on two parameters of excitation frequency and voltage.Particle image velocimetry(PIV)and boundary layer probe was used to study the in-teraction between the jet flow and the main flow.Results revealed that the promotion of both flow dilution and the power of the boundary layer are responsible for the control effect.Flow con-trol on a three-dimensional NACA633-421 airfoil was then conducted to investigate the effect of two parameters of dimensionless energy ratio Cμand the location of the actuator array.Both pres-sure and force measurements data show the ability of SSSJA to reattach the separation flow and to delay the stall at high angles of attack.The control effect gets better along with the larger val-ue of Cμ.At Cμ= 0.00168,maximum of the lift coefficient and the stall angle were increased by 5.92% and 2.5°,respectively.Chordwise location of the actuator array was proved to be a vital parameter in separation flow control.The behavior of the array located at 0.3c is better than the one located at 0.55c.The difference in the control effect is determined by the relative position of the actuator array and the separation point.Experiments were conducted at the wind speed of v∞= 16m/s and the chord-based Reynolds number of Re= 2.7×105 .