Abstract: A visualizable radioactive carbon microsphere (CMS) suspension, a preparation method, and a use thereof are provided. Every 1 mL of the visualizable radioactive CMS suspension includes: CMS: 10 mg to 500 mg; a therapeutic radionuclide with an activity of 5 mCi to 500 mCi; an imaging radionuclide with an activity of 0.1 mCi to 100 mCi; a small organic molecule: 0 mg to 100 mg; and a first solution: 0.1 mL to 1.0 mL. The preparation method mainly includes a process of allowing the CMS to adsorb the small organic molecule, the therapeutic radionuclide, and the imaging zirconium [89Zr]. The visualizable radioactive CMS suspension can realize both local radiotherapy and real-time imaging of a solid tumor lesion, and thus achieves the visualized treatment of a tumor, which provides a new radioactive CMS product that integrates diagnosis and treatment.