Starting with a few common cell lines including fibroblasts, epithelial cells, nerve cells, stem cells, lymphocytes, and germ cells, we describe the effects of terahertz radiation on the function, protein expression, and genotoxicity of different cells in detail. Around irradiation conditions and response mechanisms, some suggestions on the terahertz biology research and specific applications are put forward based on existing cytology research results. With the development and maturity of the terahertz theory in the field of biomedicine, the terahertz technology will certainly be of significance to pioneer new diagnosis technologies.