Abstract: Based on potential flow theory and the higher-order boundary element method, this study extends the 3D numerical model from a single-chamber oscillating water column (OWC) wave energy converter to a dual-chamber one, establishing a second-order nonlinear coupled air-water model. The accuracy of the numerical model is validated through the comparison with experimental data from physical models of the dual-chamber OWC device. On this basis, the hydrodynamic performance differences between single-chamber and dual-chamber OWC devices are investigated, and the effects of chamber width ratio and draft depth on the hydrodynamic performance of the dual-chamber device are analyzed. Results indicate that: under three-dimensional conditions, the dual-chamber model exhibits a significantly broader effective frequency bandwidth in the high-frequency range. When the chamber width ratio is 1∶1, the device achieves optimal efficiency. In the high-frequency region (kh≥1.0), the total wave energy capture efficiency of the dual-chamber OWC system is not highly sensitive to variations in the widths of the front and rear chambers. With draft depth increasing, the wave energy capture efficiency of the rear chamber decreases significantly, while the front chamber is less affected by draft depth variations.