Terahertz time-domain spectroscopic imaging technology has significant features such as penetration, ultra-fast time resolution, fingerprint spectral characteristics, and safe non-ionizing radiation, making it uniquely valuable for spectral analysis of material composition and non-destructive testing of industrial materials, and has become a research hotspot in recent years. This paper introduced from two directions of imaging system and imaging algorithm. At the imaging system level, it comprehensively introduced two-dimensional imaging methods such as point-by-point scanning imaging, terahertz focal plane imaging, and terahertz photoconductive array imaging, as well as terahertz near-field imaging technology that broke through the diffraction limit. At the imaging algorithm level, three-dimensional imaging methods such as time-of-flight imaging and tomographic scanning imaging were introduced. Also, the applications of terahertz technology in biomedical, non-destructive testing were listed, security inspection, and other fields. Finally, the challenges faced of current terahertz time-domain spectroscopy technology were summarized.