Using directional antennas in wireless networks has become a popular approach due to its benefits. However, since the existing MAC protocols were not designed to work with such antennas, when the existing protocols are used, the network capacity may even deteriorate rather than improve. In this paper, a neighbor discovery algorithm has been proposed for a system using directional antennas. A discovery algorithm proposed by [1] has been studied and its efficiency has been improved by making some changes. With directional antennas finding the neighbor can be a knotty problem, since when and where to point the beam is really critical for communication. Some proposed systems use GPS, omnidirectional antennas or time synchronization to solve these problems. However, the proposed system in this paper needs neither GPS nor omnidirectional antennas. It does not depend on time synchronization either.