Cancer often starts quietly and progresses very rapidly, which has led to a persistent search for more effective cancer treatment strategies. The means used in the clinical treatment of cancer mainly cover surgical resection, radiation therapy, and chemotherapy, and so on, and sometimes a combination of the above therapies will be used to eliminate cancer cells, but the overall therapeutic effect still has great room for improvement. With the integration of materials science, biology, chemistry, and medicine, the cancer nanodiagnosis and treatment system came into being. The system achieves imaging diagnosis of cancer with the help of integrated multifunctional structural combination design, can accurately transport drugs to the targeted site, and can achieve on-demand treatment according to stimulus response, which has become the general trend of future pharmaceutical development. Upconversion nanomaterials (UCNPs) have unique physical and chemical properties, and when they are combined with silica, polymers, and other substances to build a nanodiagnosis and treatment system, they have many powerful functions. This review will focus on the recent development of nanotherapeutic nanoplatforms based on upconversion nanoparticles, covering several important aspects of chemotherapy, photodynamic therapy, and photothermal therapy. We expect that this review will provide reference value for the development of accurate and efficient nanotherapies for cancer.