With the rapid progress of terahertz generation and detection technology, the application of terahertz technology has developed quickly and extended to broad fields. Especially in biomedicine, terahertz technology shows its potential in biological intervention and disease treatment. In this paper, firstly, we gave a brief introduction about terahertz radiation, its characteristics and the classifications of its generation. Terahertz radiation has the potential to non-destructively modulate the functions of living organisms because of its low energy and non-ionizing radiation characteristics, which do not cause damage to organisms. Then, we illustrated two common biological effects induced by terahertz radiation: thermal effects and non-thermal effects. Thermal effects are more likely to cause thermal damage to cells through increased temperature, whereas non-thermal effects do not cause obvious macroscopic temperature changes, but causes changes in genetic level and cellular morphological functions through other ways. Finally, on both cellular and organismic levels, we gave a detailed review of the biological effects induced by terahertz radiation on different cell types and its alteration in cell signaling. Different kinds of cells and organisms have diverse sensitivity to terahertz radiation, and the differences between the various radiation scenarios should be taken into full consideration when constructing the safety criteria. Meanwhile, the interaction mechanisms between terahertz waves and biological macromolecules need to be further investigated, and the specific signaling pathways and gene regulation of the biological effects of terahertz radiation need to be clarified. Thus, the similarities and differences in the mechanisms of terahertz action on biological organisms under different radiation conditions can be distinguished. We believe that this review will be beneficial to researchers engaged in the field of terahertz technology and biological applications.