<p>The investigation of fracture seepage characteristics in coal-rock mass is critical for the safe and efficient development of coalbed methane resources, as well as for ensuring the safety of engineering designs. This research examines the influence of fracture structure characteristics and stress environments on gas flow properties in filled fracture coal-rock mass. Samples with varying fractal dimensions and fracture apertures were fabricated using the W-M fractal function and 3D printing technology. Gas seepage tests were performed on these samples under varying confining and osmotic pressures, utilizing the HADP-II geomechanical fluid–solid coupling test system. The results demonstrate that both the fractal dimension of fractures and fracture aperture significantly influence the permeability of coal-rock mass. Specifically, permeability increases with larger fracture apertures, while decreasing as the fractal dimension increases. Moreover, the non-linear flow intensity coefficient of gas in fractures increases exponentially with the fractal dimension. A permeability coefficient, quantifying the relative seepage capacity of filled fracture coal-rock mass, is introduced. A two-parameter model is proposed to correlate the permeability coefficient with fractal dimension and fracture aperture. When the fracture aperture exceeds 1.6 mm, it exerts a greater influence on permeability than the fractal dimension. As the fracture aperture increases, it becomes the dominant factor governing the permeability of the filled-fracture coal-rock mass. The effect of confining pressure on permeability is classified into three stages: rapid decline, gradual decline, and steady stabilization. Furthermore, permeability exhibits a quadratic relationship with osmotic pressure, showing a breakthrough pressure point between stages. When osmotic pressure surpasses this point, permeability increases significantly.</p>