Terahertz communication has unique advantages in future wireless communication because of its high transmission rate and large capacity. Based on the square ring monopole element antenna, an ultra wideband (UWB)circularly polarized (CP)microstrip array antenna in terahertz band is designed. By changing the structure of the ring element antenna, the current on the antenna surface can flow asymmetrically At the same time, triangular perturbation is used to change the aspect ratio of current to realize circular polarization; The antenna array is composed of 2 × 4 antenna elements, Compared with the antenna unit, it not only increases the gain of the antenna, but also optimizes the directivity of the antenna. The simulation results show that the antenna array works at 81 GHz-112 GHz, the relative bandwidth is 32%, the maximum gain is 15dBi, and has the characteristics of wide bandwidth, simple design and low profile. It has a good application prospect in terahertz communication.