Abstract: Radioactive ¹³¹I, through the effect of ionizing radiation, is used to eliminate residual thyroid tissue, occult cancer foci, or distant metastases, making it one of the important treatments for patients with differentiated thyroid cancer (DTC) after thyroidectomy. However, ¹³¹I may cause radiation damage to the gastrointestinal tract during treatment, manifesting as nausea, vomiting, gastric and duodenal ulcers, and secondary primary cancers of the lower gastrointestinal tract. There is currently no clear and unified radiation protection strategy. Therefore, The author reviews the the absorption and accumulation mechanisms of ¹³¹I in the gastrointestinal tract, the effects of radiation damage, changes in gastrointestinal function before and after treatment, and various existing clinical prevention and treatment methods, and looks forward to future research directions. The aim is to provide a reference basis for the prevention and management of gastrointestinal radiation damage in patients with DTC treated with ¹³¹I in the future.