For the safety of electronic equipment, a two-layer barrier of cylindrical plasma array was designed to block high-power microwave(HPM). The reasonable parameters of plasma column in this experiment was designed and prepared, the diameter of single column were 25.4 mm, the length of it was 600 mm, and the plasma frequency and collision frequency were tunable according to the experiment′s need. The influence of microwave polarization, the plasma electron density, and number of the discharge unit on the performance of protection to HPM were analyzed and tested. The results indicate that the protection effect of plasma array with TM polarization is better than it with TE polarization when there is no nonlinear effect. The energy attenuation value can reach 20.9 dB and 14.7 dB respectively. The microwave transmission power decreased with the increasing of electron density to improve the protection effect. The results also show that transmission attenuation of HPM in two-layer structure is two times greater than it in one-layer structure because of the interlayer reflection.