Acoustic structure study always is the academic research interest. Diffusion ab?sorbing structure(DiflFsorber) has good research value because it has both diflFusion property and sound absorption property. Quadratic residue diffusers(QRD) structure which had good diffusion property was combined with the perforated panel which had good sound absorption property in this study. According to standard AES-4id-2001, the diffusion experiments were carried out to study QRD structure and ones composited with perforated-panels which had1 mm-thickness and perforated percentage of 3%, 5%, 8% respectively. The polar coordinate diagrams of different structure were analyzed to derive the diffusion coefficients. Results showed that the composite structure still had good diffusion performance in the frequency range from100 Hz to 800 Hz. The reflection sound energy of composite structure reduced obviously in the perforated panel resonance frequency range where there was about 2 dB reduction averagely.The study result can provide the reference for the design and development of diifsorber. Acoustic structure study always is the academic research interest. Diffusion ab? Sorbing structure (DiflFsorber) has good research value because it has both diflFusion property and sound absorption property. Quadratic residue diffusers (QRD) structure which had good diffusion property was combined with the perforated panel which had good sound absorption properties in this study. According to standard AES-4id-2001, the diffusion experiments were carried out to study QRD structure and ones composited with perforated-panels which had 1 mm-thickness and perforated percentage of 3%, 5 %, 8% respectively. The polar coordinate diagrams of different structures were analyzed to derive the diffusion coefficients. The polar sound diagrams of the composite structure reduced obviously in the perforated panel resonance frequency range where there was about 2 dB reduction averagely.Th e study result can provide the reference for the design and development of diifsorber.