It is an important approach to utilize new materials and multi-layer composite structure for improving microwave absorbing properties, especially in the full frequency range of 2~18GHz. A minimum surface reflection can be obtained via changing impedance characteristic by controlling dosages of absorbing reagents and coatings thicknesses of multi-layer materials. At present most researches are focused on double-layer and tri-layer composite absorbing coatings. In this paper, three types of composit...