Abstract: In order to control mid- to low-frequency noise, a subwavelength acoustic metasurface composed of a bending channel and an embedded aperture is proposed. A theoretical calculation model of the bending acoustic metasurface (BAM) was constructed based on the impedance transfer method and the thermal viscosity loss theory, and the sound absorption coefficient of the BAM unit at the subwavelength scale is verified. A theoretical model is utilized to study a BAM unit with a thickness of 12.00 mm and a side length of 50.00 mm, which achieves perfect sound absorption at 488 Hz. The accuracy of the theoretical method is verified by constructing a simulation model using COMSOL finite element software, and the perfect sound absorption mechanism of the BAM unit is analyzed. The results show that part of the incident sound energy is consumed by the thermal viscosity effect of the embedded aperture and the local resonance effect of the curved channel, and the remaining sound energy is coherently offset at the end of the aperture, achieving perfect sound absorption. By optimizing the geometric parameters of the BAM unit, the design of a perfect subwavelength sound-absorbing bending metasurface operating in the wideband range of 463 Hz to 579 Hz is successfully realized. Based on theory, simulation, and experiment, the influence of the over-resistance effect caused by size changes on the perfect sound absorption effect is demonstrated. This study provides a theoretical basis and method for achieving mid- to low-frequency noise control in compact noise reduction environments and offers references for engineering applications.