Abstract: The fast development of terahertz techniques is impacting the space information field. The characteristics of the terahertz wave and the applications in existence are analyzed. The applications of terahertz wave in space information field, especially in space information acquisition and transmission, are prospected. The terahertz techniques are hopefully taking advantages in space scientific observation, radar telemetry and imaging, radar early warning, inter-satellite links of constellation, wireless link in space vehicle, and TT&C link to reentry space carriers and near space hypersonic vehicles without plasma sheath induced blackout interruption.