Abstract: In order to investigate the effect of interlaminar nanofibrous membranes on permeability property of glass fiber fabrics, the super depth of field optical microscope was employed to characterize the microstructure of glass fiber fabric with different nanofiber contents. The permeability of glass-fiber preforms incorporated with interlaminar nanofibrous membranes was measured by the radial flow experiments with emphasis on the effect of the nanofiber contents on the impregnating pattern of glass-fiber preforms. The results show that the millimeter-scale regions between glass fiber bundles are filled and discretized into micron-scale regions. Both the porosity and permeability va-lues of preforms decrease with the nanofiber contents increasing. The anisotropy extent of preform was decreased as the increase of nanofiber contents. The area fraction of partially saturated regions behind resin macroscopic front increases with the nanofiber contents increasing. The area fraction of partially saturated region of preforms with the same nanofiber contents increases firstly, and then decreases with injection time increasing.