The traditional SPECT has been considered unable to quantitatively analyze due to the limitations of device performance and reconstructing algorithm. Because of the development of SPECT devices, the emergence of SPECT/CT, and the improvement of reconstructive algorithms, SPECT can be used for quantitative analysis like PET. The current quantitative SPECT researches focus on the usefulness of quantitative SPECT technology in clinical diagnosis and the guidance and evaluation of radionuclide therapy. This review summarizes the development of SPECT quantification, the current status of quantitative SPECT researches in clinical diagnosis and radionuclide therapy, as well as the limitations and advantages of SPECT quantification.