The investigation of fluid flow in fractured rocks is a key issue in underground engineering. Three sandstone specimens with different roughnesses were generated by Brazilian splitting, and the geometric morphology and aperture distribution of specimens were obtained by three-dimensional scanning technology. Fractal dimension was introduced to characterize the roughness of fractures. Seepage experiments in rough fractures were conducted to analyze the influence of fractal dimension and contact ratio on the nonlinear flow behavior subjected to different normal stresses, which proves that the Forchheimer equation can better describe the flow nonlinearity. A modified Bandis model was proposed to calculate the max normal compression displacement of fracture under normal stress. Subsequently, a new model was developed to forecast the nonlinear coefficient based on fractal dimension and contact ratio. Moreover, a semiempirical equation was established to describe the critical Reynolds number. The influence of contact areas on the seepage path was simulated by COMSOL.