Abstract: The two major forms of tritium (tritiated water vapor (HTO) and tritiated hydrogen gas (HT)) which are released into the atmosphere from nuclear installations easily pass through the stomata and root of growing crop plants to enter into their water pools by the way of HTO. The two chemical forms of tritium presented in the plant are tissue free water tritium (TFWT) and organically bound tritium (OBT) as exchangeable organically bound tritium (E-OBT) and non-exchangeable organically bound tritium (NE-OBT). OBT remains in the plant for a long time and its dose coefficients are higher than that of HTO, so the OBT may be the dominant contributor to the dose by ingestion and it is important to comprehensive studies on OBT. The study presents an overview of the definition of OBT, the determination of E-OBT and NEOBT, the formation of OBT, factors of controlling OBT production in plants and OBT concentration predictive models in plant. At the same time, the key questions in the future study on OBT in plant were described. The present study should provide some references to study OBT in the plant. In order to evaluate the radiation dose from OBT accurately, further study will be required to understand OBT measurements, mechanisms of OBT production in night and the fate in the environment.