Abstract: A kind of microwave absorbing material consisting of electromagnetic lossy substance,resonator and epoxy resin was prepared.The permeability and permittivitp of the composite were measured by using of an HP8510B microwave vector network analyzer.It has been found that the material works mainly in dielectric loss mechanism.Whereas the magnetic loss is trival in microwave attenuation.An equivalent circuit was used to simulate the composite in electromagnetic field followed by impedance analysis and power reflectivity calculation was carried out in a BASIC program. The tendancy of reflectivity variation with irequeacy determined by calculation is basically in agreement with that revealed by frequency scanning experiment performed with an HP8410C network analyzer.