As a kind of information protecting technology, material compositing becomes more and more important. The microwave properties of composite materials depend on many aspects, but stuffing is the most critical. The effect of conductive stuffing, magnetic stuffing, and the mixed stuffing are compared and analyzed in this report. It is found that conductive stuffing has the lowest absorbing behavior, while magnetic stuffing is best choice for composite. The mixing of conductive stuffing and magnetic stuffing does not result in better absorbers.