With FSS structure being prepared in the ceramicbased wedge cavity, a conductive silver paste coating process is adopted to prepare a uniform metal coating on the inner surface of the quartz fiber reinforced silica composite material (SiO2f/SiO2) wedge, and then fine structure patterns on the metal coating are etched by performing the inner surface Laser processing technology and its performance is characterized. The results show that the thickness of the metal coating is 12.08 μm, the conductivity at normal temperature and 800 ℃ is 1.57×107 S/m and 1.496×107 S/m respectively, the adhesion reaches 0 level, and the dimensional accuracy of the microstructure is 0.193 2 mm.This process can realize the preparation of a frequency selective surface on the inner wall of the wedge with a large aspect ratio, the subsequence can be applied to the preparation of the FSS structure of the inner surface of radome, antenna window and other products.