Abstract: EDXEF, as a non destructive testing tool, is especially applicable to the identification of gems and jewelry. All the different types of EDXRF, from the simplest gold analyzer to the large scale EDXRF, run on the same principles and are consisted of X ray excited source, detector, sample chamber and signal and data processing systems. The technique principles of EDXRF are explained and a few types of instruments are introduced in this paper. How to develop and use EDXRF for identification of gems and jewelry is explained, and some application examples are given.