Abstract: The accurate characterization of the through-thickness permeability of fiber preforms is the key to the computer optimization of the preparation of composites with large thickness by liquid composite molding. Mesh plate layer is an rigid component for the control of fiber thickness and the prevention of fiber’s deformation, which is placed on the upper and lower surface of the sample. The ratio of hole area for mesh plate layer is an important characteristic parameter in the measurement of through-thickness permeability K_z of fiber. Firstly, the shims used to control the thickness of fiber preforms were calibrated through experiments. On the premise of eliminating the error of fiber volume fraction, the ratio of hole area for mesh plate layer is increased through the metal mesh, the K_z of satin fabric SW220C-100b under different pressures and fiber volume fractions were measured, the concept of effective calculated area was proposed and the change rule of effective calculated area was obtained. Finally, based on the test results, the effects of injection pressure and fiber volume fraction on K_z were studied. The results show that the effective calculated area decreases with the increase of injection pressure and fiber volume fraction. The increase of fiber volume fraction will lead to the decrease of the K_z for fabric. The effect of injection pressure on K_z will be reduced by increasing the ratio of hole area for the mesh plate.