This paper gives overviews of several typical advanced detecting and imaging technologies for terahertz radar. Firstly, the history of terahertz radar technology is reviewed, and the challenges encountered in the application process are illustrated. Secondly, for five typical advanced detecting and imaging technologies, namely, single-photon detection, Rydberg atom detection, coded-aperture imaging, vortex micro-motion detection and intelligent information processing, the backgrounds, basic principles and advantages are expounded in depth. Lastly, the main achievements of this paper are summarized. These advanced techniques may have the potential to provide feasible approaches to break through the bottlenecks of the detection range and system design of terahertz radar, and further to promote the innovation and development of the detection mechanism, methods, devices and systems of terahertz technology. In the end, it is expected to provide key technical supports for the development and applications in fields such as the battlefield reconnaissance, precision strike and remote air defense early-warning.