In this paper，the preparation of the Transmission Electron Microscope (TEM) sample of NICALON (SiC)/Al preformed wires has been studied by means of Argon Ion Thinning technique. The result has shown that it is a convienient and effective method to prepare the TEM sample which contains the components with very different properties，such as the compostes of silicon carbide-aluminium. The sample of the preformed wires fabricated by the AIT method has preliminary been analyzed with the TEM.