Terahertz radiation (0.1 THz~10 THz) has attracted extensive attention of researchers recently, because of its prominent detecting ability and its noninvasive and non-ionization properties. Terahertz technologies can be categorized into terahertz imaging and terahertz spectroscopy according to the manner of detection and signal processing. With the rapid development of terahertz technology, detection of macromolecule and imaging of tissues have achieved impressive progresses. Differences of water content and variations of structure or component are essential mechanisms of terahertz biomedical imaging, which was used in identifying different biomedical tissues. Terahertz spectroscopy is an edge technology for recognizing biomolecules, cells and tissues, based on their individual terahertz spectral fingerprints by assessing their absorbance, reflective and refractive index. Based on its properties, terahertz technology has great potential ability for clinical application, especially for real-time and label- free identification. However, this technology needs to overcome several difficulties, like biological safety. In this review, we introduce the applications of terahertz imaging and spectroscopy in medical science and medical research progress, and also discuss the difficulties of terahertz technology and potential biological safety.