Fracture surface roughness and inertial effect of fluid in fractured rock masses are important factors for characterizing the hydraulic behaviors of rock masses in many rock engineering projects. This study focuses on the influences of fracture surface roughness and inertial effect of fluid on the hydraulic behaviors of 2D discrete fracture networks (DFNs), by solving a set of nonlinear fluid flow equations using the rank-one inverse Broyden quasi-Newton method. Two different boundary conditions are applied to the DFNs; and then the permeability coefficients of the models are calculated. The results show that when the hydraulic gradient J is small (<0.5), the influences of the fracture surface roughness and the inertial effect of fluid on the permeability of DFN are negligible. When the hydraulic gradient J is relatively large (>0.5), the influences of fracture surface roughness and the inertial effect of fluid on the permeability of DFN increase with the increment of the hydraulic gradient. Under two kinds of boundary conditions, the maximum influences of fracture surface roughness and the inertial effect of fluid on the permeability of DFN can be as high as 18.1% and 27.5%, respectively, corresponding to the hydraulic gradient in the range of 0.1-10. Therefore, the fracture surface roughness and the inertial effect of fluid need to be considered when calculating the hydraulic properties of fluid flow in 2D rock fracture networks, especially when the hydraulic gradient is large.