The concept of a dual-chamber oscillating water column (OWC) device consisting of a pitching mid-wall (restrained by an angle spring stiffness) is proposed and the corresponding theoretical model is established under the framework of potential flow theory. By employing the matched eigenfunction method along the common interfaces in terms of the velocity and pressure continuity, the present model can be numerically solved. A numerical strategy of successive approximation is utilized to determine the optimal turbine parameters for the optimal energy extraction. Some potential influential factors, including the linear density, installed location and draft of the mid-wall, chamber breadth and angle spring stiffness, are explored to analyze their impacts on the power extraction performance. It is found that the mid-wall in the dual-chamber structure with a relatively larger linear density and smaller draft is more beneficial for energy extraction. Under the condition that the dual-chamber structure is designed with a relatively wider size, an asymmetry configuration with a narrower front but a wider rear chamber is more recommended. In addition, a relatively smaller angle spring stiffness is advisable due to the occurrence of more satisfactory peak efficiency.