To meet the urgent need of high-speed and high-quality wireless communication in tunnel environment, the high gain antenna suitable for tunnel environment is studied. A novel approach to improve the transmission quality of signals in tunnel by using two-element phased array antenna system is presented. The phased array antenna system consists of two high gain antennas and a phase shifter. By adjusting the phase of one antenna, the minimum amplitude of the superimposed electric field strength in the tunnel can be maximized, and the average electric field strength of the signals can be increased. The simulation results show that, compared with the signals transmitted by single antenna, the minimum amplitude of the superimposed electric field strength of the signals transmitted by phased array antenna system increases by 19.6 dB at least in the axial propagation range of 3 000 m tunnel, and at least a 12.4 dB augmentation of the minimum electric field strength compared with the signals transmitted by two antennas simultaneously; the system achieves better diversity optimization effect, eliminates the deep fading caused by multipath effect, and solves the communication problem in tunnel environment.