Abstract: By regulating the pressure to cont rol the volume f raction of fibers V_f , the saturated permeability alongthe thickness of the fiber bed was measured by the unidirectional saturated flow method. The influence of pressureon V_f was investigated. Several factors which affect the permeability were studied , including V_f , the number of layers of the fiber bed , the ply stacking sequence and the kinds of fibers. The result s indicate that the degree of increaseof V_f with pressure decreases when V_f exceeds a critical value. The number of layers does not affect the permeabilityfor the unidirectional and bidirectional ply stacking while for the plain weave the permeability decreases with thenumber of layers. In addition , the kinds of fibers influence the permeability remarkably.