Abstract: In the design process of wideband sound-absorbing metamaterials, this study introduces a partially coiled-up cavity unit that combines porous materials, cavities, and curled space structures to reduce the number of structural units. This unit exhibits wider absolute and relative bandwidths, enabling excellent low-frequency broadband sound absorption performance with fewer units. Through theoretical and simulation analyses of the sound-absorbing unit, combined with optimization via a genetic algorithm, wideband sound-absorbing metamaterials composed of four partially coiled-up cavity units was designed. The thickness of this material is only 1/8 of the resonance wavelength, and its average sound absorption coefficient is higher than 0.95 within the range of 350−1600 Hz. The experimental results of the broadband sound-absorbing metamaterial align closely with the simulation results.