The permeation character is a very important quality index as to porous materials which are utilized for filtration and separation, fluid blend, gas distribution and split-flow, and so on. The token ways are introduced for the permeation behavior of porous materials, with contents including the basic concept of fluid flow, the expression of permeation character of fluid under laminar flow, the synthetical token of permeation character of porous materials, the concrete expression of osmotic coefficient of gas through porous materials, and so forth.