4T4R MIMO antennas are commonly required by operators at base stations. Existing designs of these antennas exhibit several disadvantages, such as large dimensions, high wind loads, and high costs. Thus, a new compact MIMO antenna design can help overcome these limitations. However, when two low-band 4T4R antennas come to a compact design, the electromagnetic coupling between the two arrays will increase dramatically. This can cause several problems such as ultra-wide horizontal beam width, decrease in gain, and worse inter-system isolation. In this study, a novel antenna array design method is proposed to address this issue. Using hybrid bridges, which have a typical characteristic of different frequency points with different power divides, and horizontal beam-forming technologies, a better horizontal beam width can be achieved in compact two low-band antennas. The experimental results show that, with the proposed design, the two low-band antennas exhibit a 4T4R antenna sexhibita good performance in terms of horizontal beamwidth, gain, and inter-system isolation.