Abstract: In this paper, a beam-plate coupled structure is considered. The derivation of exact expressions for power transfer and numerical computation are carried out. It is found that the SEA techniques may be appropriate for strongly coupled structures and that the general SEA result provides good agreement with the exact calculation when modal overlap is high. The derived formula is applied to predict the coupling loss factor and vibrational energy of substructures. The agreement between estimated and measured values is in most case quite good.