Abstract: The effective stress is the main reason affecting the percolation characteristics of the coal body. In order to study the evolution of percolation characteristics of fractured coal bodies around boreholes during gas pre-pumping, based on the Ergun equation and using the theory of effective stress in porous media, seepage tests of four different grades of mixed grain size fractured coal bodies were carried out to study the pore structure characteristics of different pore structure coal bodies under the action of triaxial stress, and the mechanism of the effective stress on the seepage of pore structure coal bodies was obtained. The test results show that: ① under triaxial stress, the internal seepage state of broken coal is close to non Darcy seepage. When the confining pressure is constant, the deviation from linear fitting is more obvious with the increase of axial pressure. ② The skeletal state parameters such as particle size gradation and porosity affect the permeability performance of fractured coal bodies. Based on the Ergun equation, a functional relationship between porosity and permeability and non-Darcy flow factor was derived, and the change in pore structure of fractured coal samples was obtained to fit the exponential function with the change in permeability and non-Darcy flow factor. ③ In the triaxial action, when the effective stress is loaded to the interval of 0.55-0.75 MPa, the permeability decreases sharply, especially when n=0.8, the permeability of the coal sample decreases the most, when the effective stress is greater than 0.75 MPa, the permeability decrease rate becomes smaller and smaller, the law of permeability evolution with effective stress can be expressed by expressed by the equation k=a \rme^b \sigma_e+c . Based on the above results, external stress is applied around the hole (σ) When combined with internal stress (pore pressureP), the seepage law of broken coal is closely related to skeleton deformation and pore structure change. Combined with the internal relationship between effective stress change and pore permeability, the evolution process of coal permeability around the hole in the process of gas drainage can be accurately calculated. The research on the seepage law of broken coal can be used as an important reference for the implementation of gas drainage design and effect evaluation.