〔Abstract〕 Objective To investigate the effect of ZIF-8-Pt nanoparticles on the radiosensitization of breast cancer. Methods ZIF-8-Pt nanoparticles were synthesized by chelating ZIF-8 with chloroplatinic acid(H2PtCl6). The potential, particle size and serum stability of the nanoparticles were measured. The spatial structure of ZIF-8-Pt nanoparticles was observed under a transmission electron microscope. The ability to produce oxygen(O2) by reaction with H2O2solution was measured. The uptake of ZIF-8-Pt nanoparticles by breast cancer cells(4 T1) was determined by inductively coupled plasma-mass spectrometry(ICP-MS). The toxicity of ZIF-8-Pt nanoparticles was evaluated by using MTT assay. The killing effect of ZIF-8-Pt nanoparticles combined with radiotherapy and radiotherapy alone on tumor cells was observed with MTT assay, Colony formation assay and animal treatment experiments. Results ZIF-8-Pt nanoparticles with a potent of-14 mv and a size of about 160 nm were successfully prepared. It was confirmed that ZIF-8-Pt nanoparticles were stable in 10% serum. The ability of ZIF-8-Pt nanoparticles to produce oxygen(O2) by reaction with H2O2solution was dose-dependent with particle concentration. ICP-MS results showed that the uptake of ZIF-8-Pt nanoparticles by 4 T1 cells increased with time. The clone formation assay proved that the killing effect of nanoparticles combined with radiotherapy on 4 T1 cells was related to the concentration of the particles. MTT assay and animal treatment experiments verified that the killing effect of nanoparticles combined with radiotherapy on breast cancer was better than that of radiotherapy alone. Conclusion The killing effect of ZIF-8-Pt nanoparticles combined with radiotherapy on tumor tissues is better than that of radiotherapy alone.