Abstract: Acoustic porous materials are generally applied to noise control, but they are ineffective in the low-frequency band, which cannot break through the difficulty of efficient sound absorption in the low-frequency. Perforated plate acoustic absorber is proposed because of its strong acoustic absorption ability at resonance frequency, and ordinary perforated plate is limited in bandwidth due to its structure as low-frequency acoustic absorber, and additionally needs to be combined with porous acoustic absorber or cavity to improve the performance. Microperforated plates can achieve good acoustic absorption without combining with other materials, but the strong dispersion characteristics limit their bandwidth. In order to broaden the bandwidth, in this research, a new back-cavity design concept is adopted, and a new broadband sound absorber structure is proposed, and its acoustic performance is verified by simulation and the external field distribution is calculated in the diffuse scattering acoustic field, which realizes the near-perfect broadband acoustic absorption effect in the frequency band of 380-2000 Hz. The average sound absorption coefficient reaches 0.91.