Abstract: In present work, a technique of fast atom bombardment mass spectrometry (FABMS) in conjuction with mass analyzed ion kinetic energy spectroscopy (MIKES) has been successfully applied to structural analysis of β-cyclodextrins derivatives. The results may be summarized as following:(1) FABMS exhibited protonated molecular ions by which the informations of molecular weight can be obtained;(2) However, in the MIKES of the selected protonated molecular ions, a series of characteristic fragment ions promised to give a clear, reproducible and easily evaluted picture for defining the sequence of the consistuent saccharide units of the β-clyclodextrins derivatives;(3) An additional advantage of this technique is the exclusion of interferences from impurities in the samples.