Abstract: Natural diamonds commonly contain polymeric nitrogen and have complex growing textures, whereas synthetic diamonds do not contain nitrogen or do contain single nitrogen and have typical growing textures related to the synthetic process. Using these characteristics, natural and synthetic diamonds can be distinguished. However, effective identification on melee-sized diamonds or mounted jewelry is not feasible by conventional instruments. A multi-spectral induced luminescence imaging system, GV5000 has been invented, and is described in this paper. Through improving the excitation light source, the light filter, the device configuration, and testing methods, the fluorescence and phosphorescence features of multiple melee-sized diamonds (≥0.002 ct) can be observed simultaneously. An efficient and precise method to identify colorless melee-sized natural and synthetic diamonds on the basis of the luminescent characteristics has also been established. 9015 samples were analyzed by GV5000 and screening results were checked by infrared spectroscopy, and photoluminescence spectroscopy, 97% of the natural diamonds display blue fluorescence without phosphorescence. Moreover, the luminescence of synthetic diamonds is different from that of natural ones. This new method erases the influences of size and shape of samples and increases the accuracy and efficiency of the identification on melee-sized diamonds. The screening rates of natural and synthetic diamonds are as high as 97% and 100%, respectively.