Abstract: To deal with the problem of port/starboard discrimination on the V-shaped array, a port/starboard discrimination algorithm based on focused beamforming is proposed. Given that the mirror shifts with variations in focal length while the target position almost remains constant, this algorithm distinguishes target from its mirrors by comparing angular variation amplitudes at two distinct focal lengths with a threshold. The simulations demonstrate the robustness of this algorithm against noise and array position error. Under the simulation conditions of this paper, the applicable conditions of the algorithm require that the angle of the V-shaped array be less than 170°, and the far-field target incidence direction should not be in the end-fire direction. Comparative analysis with other methods on data from the SWellEx-96 experiment confirms the performance of the proposed algorithm.