Abstract: According to the thickness and the configuration of sound-absorbing material,the cavity's acoustical impedance and the aperture's radiation acoustical impedance is analyzed in detail.Thus,to predict and optimize the sound absorption performance of the composite structure of sound-absorbing material and microperforated panel, a theoretical model is established.And the acoustical properties of several commonly used composite structures are comparatively analyzed both in theory and experiment.Good agreement between the theoretical calculations and experimental results shows the availability of the model.Taking into account the performance and economy,the composite structure of sound-absorbing material in the middle of cavity is suggested.