A graphene-based reconfigurable microstrip array antenna suitable for the terahertz band was designed in this study. The design combined the unique advantages of grapheme for impedance matching and electrical controllability in the terahertz band and the characteristics of high radiation efficiency of the reconfigurable microstrip array antenna. The array antenna unit embedded a graphene patch in the radiant patch as a switch and changed the switch's on-off and off-off states by adjusting the applied bias voltage of graphene. The antenna unit and the array antenna have an operating frequency of 5.012 THz. The antenna unit exhibits strong gain characteristics and anti-interference performance, and can realize the pattern of adjustment to 12°?24° at the working frequency. The 2×2 microstrip array antenna composed of the antenna unit can realize the pattern reconfiguration function of 0°?13°. The simulation results show that the maximum gain of the array antenna is 12.5 dBi and the maximum beam width is 51.4°. In addition, the array antenna exhibits good directivity and anti-interference ability.