The invention discloses a magnetic compound diagnosis and treatment agent capable of realizing synergistic interaction of MRI monitoring and radiofrequency ablation as well as a preparation method andapplication thereof. The magnetic compound diagnosis and treatment agent is prepared from carried solid state menthol and porous hollow Fe3O4 nanoparticles by a simple liquid and solid interconversion mediated filling method. The magnetic compound diagnosis and treatment agent enhances the radiofrequency ablation through the following two paths in a radiofrequency ablation field: 1, the inside carried menthol realizes solid-liquid-gas three-phase conversion for generating transient cavitation; meanwhile, the heat loss is blocked; the radiofrequency ablation is enhanced; 2, the porous Fe3O4 nanoparticles generate magnetic heat conversion for further enhancing the radiofrequency ablation. In addition, the magnetic compound diagnosis and treatment agent is melted along with the radiofrequency; the exchange rate and the coordination number of porous hollow Fe3O4 and water molecules are obviously increased, so that the MRI weighing effect by T1 is enhanced; the radiofrequency ablation process monitoring is realized. The product preparation conditions are mild; the simplicity is realized; the implementation is easy; no pollution exits; the yield is high; the magnetic compound diagnosisand treatment agent is applicable to industrial mass production; the clinical conversion potential is huge.