Abstract: AC-DBD actuation and NS-DBD actuation are two typical actuation forms in plasma flow control, both of which can induce spanwise vortices in the separated shear layer to control the flow. In order to understand the difference between AC-DBD actuation and NS-DBD actuation in the formation of induced spanwise vortices, flow separation control by the two actuations on the airfoil at a high angle of attack (α = 20°) is investigated numerically at Ma = 0.1, Re = 7.5 × 10⁵. The AC-DBD actuation and the NS-DBD actuation are coupled to the unsteady Reynolds averaged Navier-Stokes equations in the forms of spatially distributed momentum source term and energy source term, respectively. The two-dimensional vorticity evolution equation is used to analyze the source of the induced spanwise vorticity. For AC-DBD actuation, the body force term is the main source of the boundary vorticity variation; while for NS-DBD actuation, the baroclinic term is the main source of the boundary vorticity variation. At 1 ms after the actuation, spanwise vortex structures are gradually formed on the upper wing surface around the leading edge. Then, it is found that the main cause of the local vorticity variation for the two kinds of actuations comes from the convective term. For the vorticity transport under the two actuations, the largest difference lies in the baroclinic term, followed by the cross product of density gradient and viscous force gradient, due to the non-parallel of the fluid density gradient and the mechanical stress (viscous stress and pressure) gradient caused by the residual heat after the NS-DBD actuation. By analyzing the variation and development of the vorticity induced by the AC-DBD actuation, a reverse actuation method is proposed to improve the flow control effect of the leading-edge AC-DBD actuation.