Abstract: Terahertz(THz) band locates between the infrared and microwave and has great application prospects in the fields of national defense such as space communications, short-range tactical communications, and so on.The characteristics, categories, solutions and the key technologies involved in terahertz communication system are summarized.Research status and achievements of terahertz communication system at home and abroad in recent years are introduced, and the communication distance reaches 20 km at 0.14 THz band, the communication transmission rate reaches 105 Gb/s at 0.3 THz band.Several communication technical routes are analyzed, that conclude all electronics method, optoelectronics method and quantum cascade laser communication method, and their advantages and disadvantages are compared.Additional, the development trend and application prospect of terahertz communication technology are viewed.