Abstract: National Gemstone Testing Center collected and tested some Libyan desert glass and its corresponding imitations. The tests include infrared spectrum, Raman spectrum, X-ray powder diffraction, X-ray fluorescence spectrum, electron probe, etc..Through the tests, the authors found that: (1) There is little difference between the Libyan desert glass and the imitated products in the infrared reflection spectra, transmission spectra and Raman spectra, and it can not be distinguished exactly; (2) The Libyan desert glass has 5 200 cm^-1 absorption peak in the near infrared spectrum; (3) The chemical composition of the Libyan desert glass and the imitated products is compared and analyzed with the electron probe, which reveals that the only difference between the two is the Fe content. According to the form of water existence, it can be inferred that the formation of the Libyan desert glass is caused by meteorite impact shoal or subvolcanism.