The experimental investigation on improving the aircraft aerodynamic performance by DBD (Dielectric Barrier Discharges) plasma is described in this paper. The test has been carried out in a low speed wind tunnel with a wept aircraft model. The plasma actuators were set on the upper surface of swept wing combining with airplane body model. The test results presented include the flow field visualization by PIV (Particle Imaging Velocimetry), lift and drag characteristics under the plasma actuators off and on. The results show that the induced flow by DBD plasma may control the separation on the upper surface of the wing evidently, so that the highest stalling angle of the model increases and maximum lift-to-drag ratio rises, respectively. But with the wind velocity increasing, the effect of the plasma decreases gradually.