As the transition region from infrared light to microwave in the electromagnetic wave, the terahertz (THz) wave has its unique characteristics which are widely known. With the mature of the unit technologies such as THz radiation sources, detectors and so on, the THz technology has been firstly applied to space astronomical observation, deep space exploration and earth meteorological environment monitoring by USA, Europe and Japan. The development status of the THz technology for these applications is summarized mainly and the research status of THz radar technology and THz communication technology and their application prospects in the future are analyzed briefly.