Abstract: The achievements of diamond under high temperature and high pressure(HTHP) treatment in recent years are summarized.The objects of the treatment method include mainly the natural diamonds,HTHP synthetic diamonds and chemical vapor deposition(CVD) synthetic diamonds.The spectroscopic characteristics of these HTHP-treated diamonds are systematically reviewed and analysed,which include that of ultraviolet-visible absorption spectrum,infrared absorption spectrum,Raman spectrum,photoluminescence spectrum and fluorescence,providing the major identification.