Using metal fibrous to prepare sound absorption materials, the pore inner this material presented gradient arrangement. The gradient pore structure can be carved up two kinds, porosity gradient structure (PGS) and fiber diameter gradient structure (FGS). In this paper, the sound absorption characteristics of two kinds of these structures were studied. The results indicate that when the thickness higher than 6mm, the porosity of the PGS according to from high to low, can be enhanced the sound absorption performance in the whole frequency range at 50Hz to 6400Hz. But this law is just opposite to the thinner PGS when thickness is about 3mm. The characteristic of the FGS is when the thin fiber ahead the structure (3mm), the sound absorption performance is very well for the thicker structure in whole frequency, and when the thick fiber ahead the structure (≥20mm), the sound absorption performance is very well for the thinner structure in whole frequency. When the thickness at the range from 3mm to 20mm, there is a point of intersection between the sound absorption and frequency curves of the FGS with two kinds of arrange way.