The ideal treatment for liver cancer is radical tumor resection, but in clinical practice, liver cancer is mostly in the middle and late stages when it is detected, and only 10%-15% of the patients can be surgically removed. Radioactive particle implantation is an emerging treatment for malignant tumors in recent years, which is characterized by precise efficacy, low trauma and few complications, especially for conservative treatment of solid tumors, and has been widely used in clinical practice. When 125I particles are implanted into tumor lesions, the miniature particles continuously emit gamma rays, and the absorbed dose of local tissues can reach 140-160Gy during the half-life of 125I, thus killing the tumor. 125I particles have a killing radius of 1.7cm, and the dose decays rapidly with the increase of distance, so the normal tissues and organs absorb little dose, which achieves the purpose of both treating tumor and protecting normal tissues. The purpose is to treat tumors and protect normal tissues at the same time. The basic method of permanent inter-tissue implantation of radioactive particles for liver cancer treatment is to implant 125I particles with low-energy radiation into the tumor site and the associated lymphatic system surgically or minimally invasively under the guidance of B-ultrasound or CT, based on the computerized 3D treatment plan. Since the radiation is continuously applied to the tumor for about 6-8 months, any tumor cells that have entered the active stage are inhibited or killed by the radiation. Advantages of 125I particle implantation for liver cancer treatment: Liver cancer is not sensitive to radiotherapy and chemotherapy. In recent years, the adoption of various comprehensive treatments has improved the treatment effect of liver cancer, but the overall effect is not satisfactory and has increased the side effects of treatment. The local implantation of 125I particles can also have good efficacy for the extrahepatic metastases and intrahepatic disseminated foci of advanced hepatocellular carcinoma that are difficult to be controlled by traditional hepatocellular carcinoma treatment methods, while there are no common radiotherapy complications such as radiation pneumonia, liver function damage and bone marrow suppression. It also has certain efficacy on recalcitrant portal vein cancer embolism, as well as good pain relief effect, which obviously improves the quality of life of patients.