Carbon-14 is a radionuclide, which is a by-product in the operation of various nuclear reactor facilities. it also came from the interaction of cosmic ray with nitrogen and hydrogen in the atmosphere globally. This article elaborates the source of the 14C in High-Temperature Gas-Cooled Reactor, the amount of 14C released to the environment, as well as the forms of carbon-14. Meanwhile, the author presents the environment impact of this radionuclide. This paper concluded that 14N (n, p) 14C reaction in the fuel spheres and coolant gas is major source, and CO2 is major release form. The conclusion could provide the references and suggestions for storage, disposal and release reduction of this type of waste.