To address the issue of narrow bandwidth in existing Multiple-Input Multiple-Output(MIMO) microstrip antennas, a compact broadband high-isolation MIMO microstrip antenna and array design is proposed. By introducing cross-type capacitive fences, open slots, and shorting vias, the isolation between ports is gradually enhanced. To validate this concept, a 1×2 microstrip antenna and a 2×2 array were fabricated and measured. The measured impedance bandwidth of the 2×2 array is 44.9%, with an isolation better than 21.8 dB, showing good consistency between the measured and simulated results. Based on the 2×2 array, the applicability of the proposed decoupling structure in large-scale arrays was further verified. Simulation results indicate that the impedance bandwidth of a 2×6 array is 43.5%, with an isolation of at least 20 dB within the operating bandwidth. Therefore, the proposed decoupling solution has broad application prospects in broadband high-isolation MIMO applications and antenna arrays.