The excavation simulation and fully-coupled model of the fractured rock in the discrete element method are used to analyze the changes in fracture aperture and in the seepage flow process after excavation. The flowing discharge after tunnel excavation is used to represent the permeability of the fractured rock mass in the paper, in order to investigate the coupling effect on the permeability characteristics of the fractured rock mass. The effect on flowing discharge in the excavated cavity or tunnel by block boundary size, initial in-situ stress ratio, the fracture aperture and the included angle were studied based on the numerical test.