Currently, 90% to 98% of the natural colorless diamonds on the market are usually Ia type(Includes IaA, IaAB, IaB), colorless synthetic diamonds are mainly II type(includes IIa, IIb). The spectral characteristics of natural diamond, synthetic diamond at high temperature and high pressure(HTHP) and chemical vapor deposition (CVD) were studied by using ultraviolet fluorescent lamp, Gem Microscope, Fourier transform infrared (FTIR), ultraviolet visible near infrared absorption spectrum(UV-Vis-NIR) and confocal laser Raman spectroscopy. The Raman spectra of 1335 cm-1 were fitted by Lorentz, and the FWHMt was obtained. The results were analyzed by one-way ANOVA. The results show that the long wave fluorescence of natural diamond is stronger than that of short wave, and that of synthetic diamond is stronger than that of long wave. Cloud like inclusions, light crystalline inclusions and dark inclusions can be seen in natural diamond, Fe、 Ni metal catalyst inclusions can be seen in high temperature and high pressure synthetic diamond, and point inclusions can be seen in CVD synthetic diamond. High temperature and high pressure samples are magnetic. The infrared absorption spectra show that the natural diamond has obvious absorption peaks at 1179 cm-1, 1282 cm-1 and 1365 cm-1, belonging to IaAB type; the synthetic diamond has no obvious nitrogen related absorption at 1332-1-1100 cm-1, belonging to type II. UV-Vis-NIR spectra show that natural diamond has an absorption peak of 415 nm (N3), while synthetic diamond has no such absorption peak. The Raman shifts of natural diamond and synthetic diamond are the same. The full width at half height of natural diamond is more than 6.0 cm-1, and that of synthetic diamond is less than 6.0 cm-1. It provides a theoretical basis for the identification of natural diamond and synthetic diamond.