Abstract: Herein, we reported the behavior of the proposed infrared window for aircraft, made of photoconductive frequency selective surface (FSS) with square-slot element.First, the photoconductive coating was synthesized with a CdS:CdSe ratio of 1:1 to 5:1 and a co-dopant Cl^-:In³⁺:Cu²⁺ratio of 3.6:2.6:1.3 on sapphire substrate;next, the FSS with pre-designed square slot element was fabricated by conventioanl lithography and metal film deposition; and finally, good Ohmic contact formed at the interface of photoconductive coating and FSS structure after annealing at 400℃.The measured result show that the new photoconductive FSS displayed the highest sensitivity at600 nm, and that the center resonance frequency may increase from 13.1 to 14.2 GHz, irradiated at an average power of 200 m W/cm2.Moreover, the infrared transmitance of the photoconductive FSS window was 4% lower than that of the FSS on saphire window, being in good agreement with the resutl simulated with CST software.