Abstract: Bidirectional antennas can effectively improve signal coverage and antenna coupling efficiency, and weaken multipath effects caused by reflections from roadway sidewalls. These characteristics make them suitable for underground coal mine roadways with narrow structures and small cross-section. To address the problems of large size, low gain, and insufficient bandwidth of existing bidirectional antennas that do not meet the requirements of underground ultra-wide band (UWB) precise positioning systems, a miniaturized bidirectional beam mine positioning terminal antenna was designed. By arranging two equal-amplitude, in-phase U-shaped monopole antennas and introducing a U-shaped slot structure on the metal floor, the radiation characteristics of the bidirectional side-beam were realized while ensuring the compact structure of the antennas. Simulation and experimental results demonstrated that the antenna achieved a −10 dB bandwidth of 1 GHz (3.6-4.6 GHz), effectively covering the operational frequency band (3.7-4.2 GHz) of UWB personnel precise positioning systems in coal mines. Within the frequency band of 3.6-4.6 GHz, the antenna achieved a peak gain of 2.2-2.5 dBi, with good amplitude-frequency response.