Abstract: In the manufacture of multi-walled composite structures with fiber reinforced polymer composites by the vacuum infusion molding process (VIMP), the local multi-walled permeability is changed at the corners of multi-walled structure due to the fiber bending deformation. The effects of corner on multi-walled permeability and resin flow behavior were investigated by the visual flow experiments. The results show that, regardless of the application of distribution medium, the resin molding flow rate and overall multi-walled apparent permeability would be decreased due to the corner effect. This behavior is ascribed to the local resistance effect of the corners applied to the resin in filling process of VIMP. The corner effect can be weakened through applying distribution medium to the corners. When the distance between the corner location and the injection gate becomes larger, the overall apparent permeability will decrease first, and then increase.