In this paper, a wide-angle phased array antenna unit for high-power microwave applications is proposed. The coaxial to waveguide converter is used to realize the connection between the pyramid horn antenna and the SMA. A square coaxial block is used to improve the power capacity of the coaxial probe, and the ridge waveguide in the impedance transformation is wedge-shaped. The adjustment of power capacity is realized by adding a transition cavity structure at the back end of the waveguide, and the VSWR is reduced by introducing a matching groove structure at the bottom of the transition cavity. After the design and optimization of the simulation software, the final active VSWR is less than 1.9 at 7.5GHz-8.8GHz. The overall power capacity of the antenna is 15.88kW, which is 70.81% higher than that of common horn antennas. The scanning characteristics of the unit are simulated by the infinite array method, and the results show that the antenna can achieve ±30° conical scanning and has wide scanning characteristics. The phased array antenna unit has a simple structure, is easy to process, and has certain application value.