During the flight of hypersonic vehicle, plasma sheath will be produced on the surface due to the influence of surface shockwave. Because the plasma sheath will absorb, reflect and scatter electromagnetic waves, the communication signal will be attenuated or even interrupted, causing “blackout” problem. Theoretically, the interaction between the plasma sheath and microwave is nonlinearly changing with electric field, so there may be a suitable E-field amplitude and irradiation time interval to make electromagnetic wave transmissivity rise. For this possibility, Finite Element Analysis is used to conduct a two-dimensional coupled simulation of the plasma sheath flow field and the electromagnetic field on the hypersonic vehicle’s surface, and the change of the plasma sheath transmissivity after microwave irradiation is obtained. The plasma sheath was irradiated for 30 ns with electric field of 5×10⁴ V/m, 1×10⁵ V/m, 2.5×10⁵ V/m, 5×10⁵ V/m, respectively. The maximum transmissivity to 1.2 GHz and 1.6 GHz electromagnetic waves is enhanced after irradiation. It provides a new possibility to solve the “blackout” problem.