A new hybrid method was presented to predict vibration responses of structures in medium frequency. Finite element method was used to model subsystems with low modal density while wave method was for subsystems with high modal density. A coupled beam system was exemplified to demonstrate the details. Compared with the analytical method, simulation results validate the hybrid method. Energy density response was obtained for the subsystem with high modal density. It is found that the hybrid method produces a more precise prediction in the vicinity of boundaries.