Abstract: Fractal dimension can characterize the geometric properties of cracks and can be used to analyze the rupture surface roughness of concrete. Crack geometry plays an important role in water permeability of cracked concrete. In order to investigate this effect, a series of crack widths were obtained through feedback controlled splitting test and a variety of rupture surface roughness was achieved by adjusting fiber types and fiber contents. Water permeability test was performed to measure the permeability coefficients under different crack widths. 3D rupture surface was re-established after scanning the real rupture surface via laser scanning device. The fractal dimension was calculated based on the cube covering method. The function between fractal dimension and water permeability coefficient was established by correlating the measured crack width and the effective crack width and solving Darcy’s Law and Poiseuille’s Law simultaneously. The results show that fractal dimension calculated by the same meshing approach increases as the fiber content increases. Water permeability coefficient reduces with the rise of the fiber content. The results also demonstrate that both the absolute value of the exponential of fractal dimension and the correction factor in the function decreases with crack width increasing.