Statistical Energy Analysis (SEA) is generally used for the high frequency analysis in various areas. In the present paper a SEA-related study concerning coupled structures consisting of beams and plates is discussed. Firstly, the Fourier technique is explained to obtain the energies and power flows for excitation on the beam and the plate. Then, these are used in the Power Injection Method (PIM) to obtain the effective Coupling Loss Factors (CLFs) of the single beam-plate system. Overlapping octave bands are used in a frequency average approach. Based on the analysis for the beam-plate structure, the beam-plate-beam structure is also investigated in the SEA framework. It is found that the indirect coupling in an SEA sense may exist for such a beam-plate-beam coupled structure. The numerical result shows that its effect is larger when the dimensions of beams are similar.