The effect on the efficiency of the device of implementing a dual-chamber oscillating water column (OWC) placed over stepped bottom is analysed. The mathematical problem is formulated in the two dimensional Cartesian coordinate system under the linear water wave theory. Two different mathematical approaches are adopted to solve the associated boundary value problem (BVP), one is the method of matched eigenfunction expansion and the other is the boundary integral equation method (BIEM). The numerical results show good agreement with the analytical results. The performance of the proposed device is analysed and compared with the typical single chamber OWCs with/without step and with dual-chamber OWCs over uniform bottom profile. The present investigation shows that by considering dual-chamber OWC device on the stepped sea bottom the performance of the device can be improved significantly in wide range of frequencies, as compared with the single chamber case. (C) 2014 Elsevier Ltd. All rights reserved.