Abstract: Near-colourless melee-sized HPHT synthetic diamonds mounted as side stones in jewelry were submitted to NGTC lab and detected in 2015. Detailed analysis and testing for these jewelries were performed, The results revealed that these synthetic diamond contained Fe, Ni and other metal-bearing inclusions, which could be attracted by a strong magnet. A weak B-related absorption peak at 2 802 cm^-1 was detected in the IR spectra. Diamond View^TM observations showed blue and bluish green fluorescence with geometric shaped growth pattern and strong blue phosphorescence. Ni-related absorption lines (880, 685 nm) were detected in the UV-Vis-NIR absorption spectra. The testing results of these melee-sizedHPHT synthetic diamonds indicated “refer Ⅱ”or “refe”according to a automatic rapid diamond verification instrument (AMS). Although there were a few reports on the loose near-colourless melee-sized HPHT synthetic diamonds, it was the first time that they were found in jewelries as side stones submitted to the gem laboratory. Therefore, special attention and due vigilance should be warranted.