Carbon is the most important biogenic element in the terrestrial ecosystem, which can be converted and transported in the Earth surface system. The carbon cycle, as the link of Earth’s layers, is considered to be the most significant element geochemical cycle in the surface system. Carbon in water is mainly in the form of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC).Inland waters (including rivers, groundwater, lakes and reservoirs) play an important role in the carbon cycle, even though they account for only 1% of land surface. Changes in DIC concentration and isotopic composition of DIC in inland waters can provide clues for the study of the carbon cycle. Therefore, it has become one of the hotspots of worldwide research in recent years. This paper systematically summarized the research progress of DIC isotopes in inland waters around the world. Carbon from different sources has distinct isotopic characteristics. Therefore DIC isotopes have extensive geological applications. DIC isotopes are mainly used to qualitatively and quantitatively trace carbon sources, indicate the carbon cycle process, and determine recharge end- members.