The transmission characteristics of millimeter wave and terahertz wave in the nonmagnetic collisional plasma were investigated to meet the need of reentry aero-craft communication. The laws of electromagnetic wave transmission attenuation dependent on electron density, collision frequency, dielectric coefficient change of the antenna window material and electron frequency were obtained. The terahertz wave transmission attenuation (TWTA) is more fader than millimeter wave transmission attenuation (MWTA) in the same plasma. Both TWTA and MWTA in the plasma are at first enhanced and then impeded with increase of collision frequency of the plasma. With the increase of the dielectric coefficient of the antenna window material, MWTW is uplifted and there is a periodic oscillation in the MWTA curve, the periods of which is 5GHz. TWTA experiment was carried out on the shock tube. The results are in agreement with the calculation. Terahertz wave can be likely used as the media to resolve communications blackout on reentry aero-craft.