Closed-pore perlite and fly—ash floating beads were subjected to the surface electromagnetic modification by coating,and the modified products were respectively used to prepare cement·based composites with absorbing properties. Then,the electromagnetic wave reflectivity of the composites was measured,and a suitable proportion of the materials used for coating was determined to obtain composites with stable absorbing properties.Moreover,the electromagnetic wave refleetivity of the cement-based composites respectively with modified perlite and graphite(or ferrite)in S~C and X~Ku wavebands was comparatively investigated,and the microstructure of the modified per-lite was finally observed by means of SEM.The results show that graphite and ferrite,which are uniformly distribu-ted on the closed-pore perlite surface with a alternately-distributed continuous glaze surface and a special honey-comb structure,form a resonant absorber with high performance,and that the closed-pore perlite modified by coa-ting effectively improves the absorbing properties of cement—based composites and broadens the -10 dB bandwidth.