Abstract: Spherical Au nanoparticles were synthesized by thermal decomposition at high temperature, then were coated with a layer of MnO to form Au@MnO core-shell nanomaterial. MRI results show that the paramagnetic MnO shell could accelerate the longitudinal relaxation of proton in water molecules, with magnetic resonance imaging diagnostic capability; photothermal conversion results indicated that Au core possessed obvious near-infrared absorption and good photothermal heating effect. The as-prepared Au@MnO core-shell nanomaterial was injected into mice through tail vein, and it was found that the magnetic resonance signal in tumor area enhanced significantly to 181%, which was obviously different with the surrounding normal tissues. Under 808 nm laser irradiation, tumor temperature increased rapidly to about 60℃. These results provided an experimental example of Au@MnO nanomaterial for tumor diagnosis and treatment.