Abstract: With high-pressure-high-temperature (HPHT) synthetic diamond method gradually becoming mature, people have successfully improved its colour by adding boron or other getters to prevent yellowish tune brought from nitrogen-related impurities. However, the existence of boron induced a special luminescence phenomenon for these diamonds. Therefore, when excited by short-wave UV light, these synthetic diamonds exhibit fluorescence and/or phosphorescence in different colours. Taking advantage on these properties can help us identify this kind of synthetic diamonds in gemmology field.DiamondView^TM, micro middle-infrared spectrometer and photoluminescence spectrometer were resorted to collect fluorescence/phosphorescence images and spectra on a batch of China-produced colorless HPHT synthetic diamonds. The DiamondView^TM images show the greenish blue phosphorescence and sustain times varies with each sample. In dark environment, the phosphorescence can be observed last more than 10 minutes by naked eyed. The emission spectra suggested that the greenish colour depends on the band centered in 470 nm with 500 nm shoulder. The band can be excited under short-wave UV light ranged from 215-250 nm among which 230 nm is the most effective.The intensity would decay gradually over time. The middle-infrared spectra further pointed out that absorption coefficient on 2 802 cm^-1 boron-related peak negatively correlated with the decreasing rate on 470 nm phosphorescence. Above experiments revealed that absorption in 2 802 cm^-1 would affect phosphoresce properties.