Abstract: The mirror-reflection infrared spectrum technique has abroad application in gemmology. It can not only measure the finger print spectra of the gems which can’t be measured by the infrared trans mission technique, but also by using the back mirror-reflection it can measure the spectrum of function group which is very low in content in the gemmineral, which has the important significance for the identification. The dist ortion of mirror-reflection I R spectrum resulted from anomalous dispersion can be removed by the K-K transf or mtechnique and the same spectrum as the trans mission I R spectrum can be obtai ned. The mirrorreflection I R spectrum technique has a lot of advantages incl udi ng non-special prepared samples, simple instrument, low cost and easy operation, and it isn’t li mited by the surface nat ure and transparency of the samples. It is an ideal undestr uctive testing mothod with a wide application.