Abstract: In the present work, the dielectric-barrier-discharge (DBD) plasma actuator is employed to study the flow structures over a flat plat. A simplified DBD plasma model is established by treating the plasma effect as the body force to be implemented into the Navier-Stokes equations and solved by the large eddy simulation (LES) method. The results show that a series of vortex pairs in the dipole formation and in a periodic distribution are generated in the boundary layer as soon as the DBD plasma actuator is applied to the flow over a flat plane. They enhance the momentum transfer between the near wall region and the free stream. At the location of x=0.5b downstream the actuator, the maximum induced velocity is found to follow a power-increased law for the actuation strength applied.