Abstract: 5G network technology can meet the high requirements of cyberspace development in the performance of communication platforms. Massive MIMO (multiple-input multiple-output) antenna array is one of the core technologies of 5G. The mutual coupling effect of massive MIMO antenna arrays will greatly reduce the Shannon capacity. In future 5G antenna systems, the biggest challenge is how to effectively eliminate the mutual coupling between the antennas in the array. The same antenna radiation pattern may correspond to many different forms of antenna. These different antennas have the same radiation characteristics but different scattering characteristics. To reduce the mutual coupling of large-scale antenna arrays, antenna elements with low scattering characteristics should be selected. To address the mutual coupling problem of large-scale array antennas, the scattering characteristics of antenna elements are studied. On the basis of the “invisible” minimum scattering antenna in the open-circuit state, the scattering matrix of the minimum scattering antenna connected in series with a quarter-wavelength transparent network is deduced. Findings indicate that this setup is the suitable minimum scattering antenna in the short-circuit state. The scattering formulas of a corrugated horn antenna under short-circuit, open-circuit, and matching loads are deduced by using a series network model. On the basis of these formulas, the calculation methods of excess scattering, associated scattering, and mismatched scattering components of the antenna are deduced. Scattering measurements of an X-band corrugated horn antenna under short-circuit, open-circuit, and matching loads are performed. According to minimum scattering antenna theory, the excess scattering, associated scattering, and mismatched scattering of the antenna are separated. Then, the maximum and minimum scattering of the corrugated horn antenna are calculated by using the separated scattering components; the calculated minimum scattering is much lower than the scattering when the antenna matches. Scattering measurements of corrugated horn antenna under preset loads are carried out by using a sliding short-circuit device to apply variable loads. The measured values are consistent with the calculated maximum and minimum scattering values, thereby verifying the correctness of the research on the scattering characteristics of the element antenna. Results show that, in the design of a large-scale array antenna, not only the radiation characteristics of the antenna but also the scattering characteristics of the antenna should be considered to reduce the mutual coupling effect of the antenna.