Abstract: Millimeter-wave signals make the integration of antenna arrays technology possible, which can be employed to implement beamforming. However, with the increasing of antenna elements, the complexity of beam searching will also significantly increase. By fully exploring beam characteristics generated with different numbers of array elements, an efficient beam searching algorithm is proposed relying on a novel conception of dividing and conquering. By increasing progressively the number of antenna elements, the search space is noticeably reduced, and the optimal beam pair can be iteratively discovered. Compared with the existing popular schemes, the proposed algorithm can significantly reduce preamble transmissions accompanying energy consumption. Numerical simulation results validate the superiority of the proposed algorithm.