At present, about 80 percent of rough sapphire mined from the Mogok mine in Myanmar must be optimized before being put into the market, mainly heat treatment. In this paper, the sapphire from Baw-mar mine, Mogok, Myanmar is heat treated with different temperature regimes, and electron microprobe, X-ray powder crystal diffractometer (XRD), ultraviolet-visible-near infrared spectrometer, fourier infrared spectrometer and laser raman spectrometer were used to compare the spectroscopic characteristics before and after heat treatment. The results show that after heat treatment at 1 300℃, all XRD peaks of sapphire with 2θ<60° begin to shift to low angle direction, and the ratio of unit cell parameter c/a decreases with the increase of heat treatment temperature, which is presumed to be related to the distortion of its crystal at high temperature. The main chromogenic elements of sapphire in Baw-mar mining area are Fe, Ti and V, among which Fe and Ti together cause it to be blue, V makes it slightly green, and the gray color of some samples is mainly caused by Ni. After the heat treatment, the charge transfer of Fe²⁺-Ti⁴⁺ is enhanced, and the charge transfer of Fe²⁺-Fe³⁺ is weakened, resulting in an enhanced 585 nm ultraviolet absorption band and a weakened absorption peak at 746 and 764 nm. At the same time, the color of the sample turns blue and the gray tone weakens. In the infrared spectra, the sample appears at 1 988, 2 123 cm^-1 diaspore hydroxyl frequency doubled vibration absorption peaks and 3 619, 3 696 cm^-1 kaolinite outer hydroxyl and inner hydroxyl vibration absorption peaks. After the heat treatment, the diaspore and kaolinite are completely dehydrated, and the crystal structure is destroyed, resulting in the disappearance of all the hydroxyl absorption peaks. After heat treatment at 1 100℃, the Raman peak at 1 324 cm^-1 appeared and gradually increased with the increase of temperature. It is speculated that it is caused by the reaction of molten borax and Al₂O₃ at high temperature to form glassy substances along the cracks and enter the interior of the sapphire. The research in this paper also provides ideas and basis for further discussion of its color changing process.