Abstract: Based on the two-dimensional circumferential decomposition method, this study addresses the numerically fast calculation of the three-dimensional scattering sound field for the near-bottom target under the non-axisymmetric background of the total field. Moreover, the method is applied to study the acoustic scattering mechanism of a near-bottom suspended elastic sphere. The frequency-angle spectrum and frequency-height spectrum of the near-bottom elastic sphere target scattering have been calculated based on the ray acoustic superposition theory of the four-path coupling model between the target and the seabed. Importantly, these calculations account for the additional echoes generated by the interface. Additionally, the accurate prediction formula for the alternating bright-dark interference fringes of the coupled scattering sound field is given. Through analysis and verification of both numerical calculations and experimental results, the propagation law of target mirror reflection, elastic waves excited in the elastic target body, and seabed reflection waves coupling with each other and their influence on the total field is explained when the glancing angle and suspension height of the target change. Furthermore, the mechanism of target scattering sound field intensity fluctuation caused by changes in suspension height and glancing angle is analyzed.