Abstract: Plasma sheath surrounding reentry vehicle influences the transport of the communication signal, even the results in the communication blackout. The characteristics of the reentry plasma sheath are analyzed in this paper. Based on the theory of the wave propagation in the plasma and with consideration of the inhomogeneity of the electron density in the reentry sheath, a model is built to investigate the reflection and the absorption of the electromagnetic wave by the sheath. With the model, an object-oriented software is developed to calculate the reentry communication blackout and to investigate the factors that determine the communication blackout. It is shown that the plasma electron density and its distribution determine the transport of the communication signal. In a certain range of the plasma electron density the blackout effect exists, and it can significantly weaken the signal attenuation to decrease the electron density.