In civil engineering，hydraulic engineering and nuclear wastes disposal engineering，great attention is focused on the influence of stress state on rock permeability. The permeability coefficients of clayey siltstone and brown mudstone were investigated by the transient pulse technique in the complete stress-strain curve. The results show that：(1) The permeability coefficient of clayey siltstone decreases in the stage of elastic deformation but increases in the stage of plastic deformation and the fractured phases. The permeability coefficient on the direction vertical to the bedding plane is larger than that on the direction parallel to the bedding plane. (2) The permeability of brown mudstone decreases in the stage of plastic deformation but keeps stable in the stage of creep deformation. The permeability coefficient on the direction vertical to the bedding plane is similar to that on the direction parallel to the bedding plane. Combined with the stress-train curves，it can be deduced that in the stage of elastic deformation，the permeability coefficient of clay siltstone is mainly influenced by porosity and small cracks；and in the stage of plastic deformation and the fractured phases，it is mainly influenced by small crack. In the complete deformation process，the permeability coefficient of brown mudstone is influenced by porosity and small cracks，boty effects are not distinguishable.