The model for the effective electromagnetic coefficients is established. The influence of the volume ratio of the outer layer and the inner on the absorption and the characteristic impedance is discussed. The microstructure of the coated absorbent is designed. Sol-gel method is used to prepare the coated radar absorbent. It is shown by the theoretical and experimental results that the absorbing ability of the coated magnetic absorbent has be improved greatly, and the absorbing band below -8 dB is about 9 GHz.