Based on electric resonance principle and image theory, a new type of periodical grounded edge-coupled split ring resonator （SRR） structure is designed in this paper. Then the proposed metamaterial structure is used to suppress the mutual coupling between elements in microstrip array. Compared with the traditional structures for suppressing mutual coupling, the proposed metamaterial structure has not only small size （to be specific, a small thickness of 0005 operation wavelength）, but also the ability to suppress the mutual coupling with excellent performance （-168 dB）. The obtained results indicate that the metamaterial has an enormous potential in designing compact and high-performance microstrip arrays.