Abstract: In this paper,sound absorbing property of mutilayer complicated microperforated structure is analyzed, and formulae for its acoustic impedance and absorption coefficient in diffuse field were derived. Analysis shows that simply apply structure parameters from results of normal sound field for mutilayer structure in diffuse field could be misleaded.The theoretical model developed in this paper was proved by experiments in reverberation room and shows it can predict the absorption of varies mutilayer structures in good accuracy.The therefrom developed software can be easily used for designing of mutilayer complicated microperforated structure.