Abstract: Frequency selective metamaterials are promising advanced radome materials. Lightning shielding failure rate of this kind of metamaterial is high, which restricts its engineering application. Choosing the optimal distance between the lightning diverter strips is the key to guarantee the metamaterial electromagnetic transmission efficiency and the success rate of lightning shielding. The length of surface discharge on the skin under the impulse voltage is one of the factors determining the optimal distance between the strips.Based on the actual radome structure, this paper designed a test platform for discharge along the square ring resonator frequency selective metamaterial skin surface. The influences of grounding position, discharge times and skin material on the length of surface discharge（horizontal direction） on the skin were studied. The micro damage morphology of the skin along the surface was observed after discharge. The surface resistivity and the charge distribution on skin surface were measured.Based on the above observation and measurement results, the test results of surface discharge on the skin were analyzed.Results show that, the influence of grounding position on the length of surface discharge on the glass fiber reinforced epoxy resin skin is small. With the increase of discharge times, the length of surface discharge on the skin grows. The surface resistivity influences the length of surface discharge obviously,with the decrease of product of surface resistivity and dielectric constant, the length of surface discharge increases. It is hopedthat research results could provide theoretical reference for lightning protection on metamaterial radomes.