In order to explore the effect of surface of dielectric barrier discharge (SDBD) plasma on flow separation of backwardfacing step. We used the proposed plasma effect on fluid numerical simulation method by Suzen. Andapplied Fluent software to calculate the electric field distribution and charge density distribution equation. By compared the results with the existing experimental data and verify the accuracy of the simulation method. On this basis, plasma excitation was applied to the front of the step to observe its control effect on the flow separation of the back step. The simulation results show that the plasma aerodynamic excitation can significantly reduce the backwardfacing step flow’s reattachement distance. When the incoming flow’s wind speed is 1 m/s, the reattachment length can be reduced by 53.92%.When the incoming flow’s wind speed increases gradually, the effect of plasma aerodynamic excitation control gradually weakens. When the excitation intensity is increased, the control effect is enhanced.