Abstract: Tritium, a common radionuclide produced in nuclear reactions, is highly mobile in the environment and in all biological systems, and the health effects of tritium on humans and other organisms are of increasing concern. Therefore, understanding the toxicological effects and carcinogenic effects of low-dose tritium is important for assessing its potential impact on human health and developing protective strategies. In this paper, we review three aspects of tritium: its sources and modes of existence, toxicological effects of low-dose tritium, and carcinogenic effects of low-dose tritium, and discuss the effects of low-dose tritium on biological health.