Abstract: The gemmological characters and colouration of hydrothermal synthetic rubies from Guilin are presented, using the IR, UV VI and EPMA testing methods. The research shows that the infrared absorptions by Al-OH and H-O in the hydrothermal synthetic rubies from Guilin, in the direction vertical to the 2243, are dominated the stretching vibration weak peaks at 3307, 3231, 3184, 3013cm^-1 and 2364, 2348cm^-1, and can be considered as an important indicator for the identifying hydrothermal synthetic rubies from Guilin.