Abstract: Malignant tumors are serious threat to human health. The way to treat cancer include surgery, radiotherapy and chemotherapy, etc. ¹²⁵I is a radionuclide with a longer half-life (T_1/2=59.7 d) and release of low-energy gamma rays (27 keV) by electron capture. ¹²⁵I is suitable for brachy therapy in nuclear medicine and could be prepared as seed source widely used in clinic. ¹²⁵I-seeds could be implanted into tumor tissue by surgical implantation. The therapeutic methods are simple and less invasive and have broad application prospects which show significant curative effect in lung cancer, pancreatic cancer, prostate cancer and other solid tumors. This paper reviews the research progress of the preparation of ¹²⁵I and ¹²⁵I-seeds, the ¹²⁵I-seeds in treatment different types of tumors. The development trend for of ¹²⁵I-seeds sources application is also been discussed.