Abstract: PET(Positron Emission Tomography)is the most advanced technology now in nuclear medicine, it integrates many up-to-date technologies in nuclear science, electronics, computer, data processing, etc., PET set is also the most important imaging diagnosis devise in clinical medicine, which now plays more and more important role in the diagnosis of human cancer, myocardial and brain disease. Using the homemade 32-Ring PET as an example, the general working principle, the functional structure are overviewed in this article, and its clinical application is demonstrated as well.