Abstract: Zhengguamycin A_5, A6, A2, Demethyl-A2, B2 and their complex withcopper were studied by Fast Atom Bombardment Mass Spectrometry in ourlaboratory. They all showed similar cleavage rule. A simple and rapid methodhas been established for the identification of Zhengguamycin according to therule. It is significant that structure information of pentapeptide, disaccharideand terminal amine in the molecule can be observed on the spectra.