<p>Gas cylinders are regarded as critical acoustic equipment in underwater diver operation systems. The highlight echo intensity from the cylinder body and edges is recognized as a major contributor to the overall target acoustic scattering. In response to the practical requirements for acoustic feature identification and detection of small underwater targets, refined modeling and mechanistic analysis of acoustic scattering are considered to be of significant applied value. A three-dimensional numerical model for acoustic scattering of a dual-gas-cylinder system under specific working conditions was constructed using the Boundary Element Method (BEM). The full-aspect target strength frequency responses under both horizontal and vertical orientations were calculated. The coupling mechanism among local strong scattering sources such as the cylinder body, edges, and valve structure was analyzed. The energy superposition and the generation mechanism of interference fringes between multi-body configuration scattering and single-target scattering were revealed. It was shown that even under dual-target coupling conditions, the resonant modal features of a single gas cylinder can still be effectively extracted. A quantitative mapping relationship from geometric configuration and spatial arrangement to resonant frequency response was established. A theoretical framework suitable for predicting acoustic scattering from multiple small targets was developed. To validate the model’s capability in characterizing the multi-target coupling scattering mechanism, full-scale experiments were carried out in a controlled lake environment. By comparing the spectral structure and directivity of echo signals within the 40 ~ 80&#xa0;kHz range, the effectiveness of the proposed coupling mechanism model was confirmed in a realistic underwater acoustic environment.</p>