The influence of embedded cell on the formation of broad acoustic band-gap in the three-component crystal slab is analyzed by calculating the acoustic transmitted energy of the epoxy resin matrix with one embedded cell, which consists of the elastically soft rubber coat and the inner core steel cylinder. It is found that the broad band-gap in the three-component crystal slab results from localization of the acoustic wave energy in the rubber coat for a broad ultrasonic frequency interval. Comparison between experiments and calculations shows good agreement.