Abstract: In order to investigate the unsaturated impregnation property of resin along the thickness of fiber stacks at high temperature during the process of resin film infusion(RFI), the influence factors of the flow front of resin were studied, and the effects of the primary factors on the impregnation velocity of liquids along the thickness of glass fiber weaves and the rules were tested and analyzed by using the self-designed equipment. The results indicate that the resin infusion along the thickness of fiber stacks is one-dimensional flow, and the impregnation velocity of liquids can be increased by increasing the vacuum pressure, raising the temperature of resin and reducing the volume fraction of fibers. In addition, the impregnation behaviors of E-51 epoxy resin at 70 ℃ and silicone oil at room temperature along the thickness of glass fiber plies are almost homological.