According to the current development trend of wireless communication systems, a miniaturized dual-unit ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna with high isolation is designed, and its overall size is only 18 mm×22 mm× 1 mm. The antenna’ s radiation patch adopts a rectangular structure etched with a hexagonal star, and a “ w” shape and a small rectangle are cut out on the upper and lower positions on the right side of the antenna to realize the broadbandization of the antenna. The high isolation of the antenna is achieved by using defective ground (DGS) structure and etching two semicircular slots of equal radius at the top of the ground plate. The simulation results are basically consistent with the actual measurement results. The final operating bandwidth of the antenna is 2. 75~ 10. 64 GHz (relative bandwidth reaches 117. 85%), and the isolation within the bandwidth range is greater than 22 dB, and the envelope correlation coefficient (ECC) is less than 0. 015. Therefore, the designed antenna is not only extremely small in size, simple in structure, but also good in performance, and can be widely used in wireless communication systems.