Abstract: Carbonyl iron powder was modified by Silane coupling agent（KH-560）,and carbonyl iron powder/epoxy resin composite material was prepared using epoxy resin as matrix and carbonyl iron powder as absorbing agent.The modified carbonyl iron powder was characterized by TG,IR etc.The electric volume resistivity,voltage breakdown strength and absorption loss of the carbonyl iron powder/epoxy resin absorber were measured,and the characteristics of isolator using the prepared absorber was tested.The results show that the dispersivity of carbonyl iron powder in epoxy resin matrix is good and the degree of insulation among carbonyl iron powder in the composite is quite high.The absorber has electric volume resistivity of 4.99×10⁸Ω·cm,breakdown strength of 700V/mm and absorption loss of 1.8 to 7.8dB/mm in frequency range of 6 to 18GHz.The isolator employing this composite absorber has a VSWR≤1.6,insertion loss≤1.2,isolation≥11dB,relative bandwidth of 100%.