Focused ion beam (FIB) system is a powerful microfabrication tool which uses electronic lenses to focus the ion beam even up to nanometer level. The FIB technology has become one of the most necessary failure analysis and failure mechanism study tools for microelectronic device in the past several years. Bonding failure is one of the most common failure mechanisms for microelectronic devices. But because of the invisibility of the bonding interface, it is difficult to analyze this kind of failure. The paper introduced the basic principles of FIB technology. And two cases for microelectronic devices bonding failure were analyzed successfully by FIB technology in this paper.