Aimed at the problem that the communication blackout usually happens when a hypersonic vehicle voyage closes to the space, a model of plasma sheath is established according to the data provided by radio attenuation measurement C (RAM C) voyage experiment. Through numerical calculation, the principle of interaction between plasma and terahertz wave is analyzed, and the properties of terahertz wave propagation in plasma sheath are obtained by changing the parameters of plasma including plasma thickness, plasma density, plasma collision frequency and terahertz wave incident angle. The simulation shows that taking the terahertz frequency band as communication frequency band in near space, this is advantageous to the solution of communication blackout problem in the value of attenuation less than 30 dB at the atmospheric window of 0.22 THz. The result can be used as reference for design of communication platform in the near space.