Radar in terahertz regime has great advantages compared with microwave radar and infrared detector, such as high range resolution, strong penetrating ability, low intercept probability and strong anti-interference ability, etc. On the basis of analysis of characteristics and advantages of terahertz radar, research progress of terahertz radar systems reported recently is introduced first. Then, study of target scattering characteristics and radar imaging technologies in terahertz regime is reviewed and commented. Some of the key technologies and main research directions related to the terahertz radar are pointed out correspondingly. Key parameters of terahertz radar system are analyzed and simulated concerned with military applications of space target detecting and radar seeker, which helps to provide reference for the application development of terahertz radar.