Abstract: In order to study the permeability characteristics of polypropylene fiber reinforced concrete (PPF/PC) after damage and cracking, cracks with different width (100-400 μm) were prefabricated by disc splitting test, and the influence of PPF content on the crack tortuosity was compared. The permeability of concrete after damage was studied by using a self-designed permeability test device, and the change law of damage permeability of the concrete under different fiber contents and water pressures was analyzed. It is found that after adding PPF, the brittleness of concrete is lower, the internal cracks are easier to control, the crack tortuosity is higher than the ordinary concrete (PC), and is proportional to the fiber content; under the same water pressure and the same effective crack width, with the increase of PPF content, the damage permeability of concrete decreases, and the existence of fiber can effectively improve the impermeability of concrete after damage. Under the same water pressure, the damage permeability of concrete specimens with the same amount of PPF is directly proportional to the effective crack width; under different water pressures, the damage permeability of PPF/PC with the same PPF content decreases with the increase of water pressure under the same effective crack width; the modified Poiseuille model can better evaluate the damage and permeability characteristics of PPF/PC.