Abstract: Radionuclide is the basis of nuclear technical application in nuclear medicine. Radionuclide therapy is a representative treatment way for various diseases including cancers, which uses the decay energy of various type of particles released by radionuclide to kill diseased cells and achieve therapeutic purpose. The decay particles have significant differences in range depending on the characteristics, which are suitable for kinds of therapeutic purposes. The emission of α-particles would be ideal for treatment of single tumour cells or micrometastasis, whereas the emission of β-particles would be more suitable for larger metastasis or small solid tumours and Auger emitters could be used for therapy when the carrier molecules carry the radionuclide closely enough to their DNA. The type of decay, half-life, production, supply, and properties of radionuclide determine its clinical application and limits. Radionuclides for routine clinical use should be readily available and inexpensive, from this point of view, neutron-rich radionuclides produced in reactors are usually cheaper than accelerator-produced radionuclides. This paper analyzes the main factors which determine the therapy application of radionuclide in clinical and prospects for the therapy application of some nuclides, which provide reference for the development and clinical application of radionuclide therapy.