In this study, the effects of particle size and porosity on electromagnetic and electromagnetic wave absorbing properties of an epoxy-ferrite composite were investigated. The complex permeability, permittivity and electromagnetic attenuation value of the composite were obtained using an impedance/gain phase analyzer (HP4194A) and a network analyzer (HP8753C) in the frequency range from 1 MHz to 5 GHz. The complex permeability of the composite and the real part of permittivity increased with increasing the particle size of ferrite. The imaginary part of permittivity was independent of the particle size. The relaxation spectrum of fille complex permeability had gotten broad with increasing the porosity of composite. The particle size distribution had an effect on the complex permeability of composite. However the complex permittivity was independent of the particle size. The attenuation frequency mange could be changed by controlling the particle size and the particle size distribution of ferrite at the given ferrite content.