Radiotherapy is a mainstay treatment for malignant tumors in clinical. However, enhancing radiation damage to tumor cells meanwhile sparing normal tissues is still a great challenge in radiotherapy. Nanomaterials with high atomic number (Z) values are promising radiosensitizers by promoting the radiation energy deposition in irradiated tumor cells, thus enhancing the therapeutic ratio of radiotherapy. In this review, we described the mechanisms of high-Z element radiosensitizers and systematically summarized the recent progress on metal-based nanomaterials, including high-Z metal nanoparticles, metal-organic frameworks (MOFs) and other high-Z-containing nanomaterials. Finally, further potential and challenges in this field were discussed.