Abstract: Acetylspiramycin (AC-SPM)has been shown to consist of four closely related components.Based on the data of their spectra,the four components,which were isolated form Chinese made AC-SPM by classical column chromatography,have been elucidated as diacetylspiramycin Ⅱ,diacetylspiramycin Ⅲ,monoacetylspiramycin Ⅱand monoacetylspiramycin Ⅲ,respectively.