Terahertz wave has prospects and application prospects, but long-term exposure to terahertz wave may have adverse effects on human body, especially on young children and pregnant women. At present, more research is needed to understand the long-term effects of terahertz waves on human body. According to the existing research, the biological effects of terahertz waves mainly involve thermal effects and non-thermal effects. Thermal effect refers to the temperature rise caused by the absorption of terahertz wave energy, which may cause thermal damage to tissues. Non-thermal effects include effects of ionizing radiation and non-ionizing radiation on cells and genes. Although there is no clear evidence that terahertz wave is harmful to human health, it is suggested to avoid long-term and high-intensity terahertz wave irradiation, especially for young children and pregnant women, in order to protect human health.