The plasma sheath produced in the progress of entry or reentry flight has attracted much attention as it would impact the propagation of electromagnetic wave. This plasma sheath is a group of weakly ionized gas in general and has the ability to influent the communication between aero craft and ground. Sometimes the existence of this plasma sheath even cloud cause the communication blackout which is not desirable. To improve this problem plenty of researches have done, some of the researches mentioned that raising the wave frequency could be one way. The development of intensive terahertz sources broke up the restrain of electromagnetic wave in microwave range, there comes out several researches on the interaction between terahertz wave and plasma. Computational fluid dynamics was used in numerical simulating of a thermodynamics and chemical nonequilibrium flow over the aero craft to calculate the electromagnetic characteristics of plasma layer. Four flight scenes and different incidence forms were taken to discuss the interaction between terahertz wave and plasma sheath. And the propagation of terahertz wave along with different paths was discussed. From the simulating results, terahertz wave is capable to transmit in the plasma sheath with high electron density when the flight height is lower.