This invention discloses a near-infrared fluorescent magnetic microemulsion nanoparticle, its preparation method, and its application in tumor therapy. The invention involves embedding magnetic nanoparticles together with near-infrared fluorescent quantum dots or near-infrared fluorescent organic dye molecules into an oil-in-water microemulsion. The microemulsion can also encapsulate anticancer drugs. Through the magnetic guidance of the magnetic nanoparticles, the near-infrared fluorescent substances embedded within the microemulsion are targeted to the tumor site or fixed there. Under the excitation of near-infrared light, the thermal effect generated by the near-infrared fluorescence emitted from the near-infrared fluorescent substances is used to kill tumor cells. Utilizing near-infrared fluorescent quantum dots, it is also possible to synergistically destroy tumor cells through the photoexcitation-generated highly active *OH and •O2 radicals along with the thermal effect. The thermal effect, the cytotoxic action of the anticancer drugs, and the photocatalytic activity of the quantum dots work together to synergistically destroy tumor cells. The present invention is of significant importance for the treatment of malignant tumors in clinical practice and has broad application prospects.