The acoustic coating can be used by submarines to absorb sound waves and is a primary means of countering active sonar detection.With the continuous advancement of underwater detection technology, current acoustic coatings are being developed to achieve low-frequency broadband sound absorption in deep-sea environments.Traditional cavity-type coatings, due to their narrow absorption bandwidth and poor resistance to water pressure, are no longer able to meet application requirements.A novel sound-absorbing structure based on a circular tube honeycomb configuration was proposed in this paper.According to the equivalent layered medium theory, the theoretical solution of the absorption coefficient was derived using the transfer matrix method.A COMSOL finite element model was established to compare the theoretical results with simulation ones in detail, verifying the reliability of the finite element modal.The sound absorption mechanism was systematically analyzed, revealing that the introduction of the honeycomb structure induces shear vibration in the polyurethane, which enhances panel vibration and facilitates the conversion between longitudinal and transverse waves.Their coupling effect increase sound energy dissipation, achieving broadband sound absorption in the range of 1 091 Hz to 10 000 Hz, with an average absorption coefficient of 0.869.Both material parameters and the honeycomb structure impact the sound absorption performance.Higher loss factors and thicker honeycomb walls improve the sound absorption effect.The sound absorption performance under hydrostatic pressure was studied, and the results indicate that the structure can maintain its absorption stability under water pressure as high as 5.0 MPa.