Abstract: In order to investigate the seepage change in the microstructure of coal, taking Xinjiang Dahuang Mountain’s gas coal as an example,using CT scanning and 3D reconstruction technology,a 3D coal skeleton struc- ture model with pores and fissures is established. On this basis,a fluid solid coupling model which can reflect the dy- namic seepage process is constructed. Then combined with the ALE algorithm with Navier-Stokes control equation,the numerical simulation is carried out. The results show that in the process of seepage flow,there is a velocity peak and a steady flow velocity at the each point of the pores and fissures. Compared to the fracture structure,the poor connectivity of pore structure increases the loss of fluid kinetic energy at the front of the model and slows the flow of fluid in the fol- lowing pores. The initial flow velocity affects the variation trend of flow velocity and fluid density at the inlet,and also changes the peak velocity variation in the fracture. When the initial velocity is lower than 0. 03 mm / s,the peak value of velocity in fractures shows a trend of “first increasing,then decreasing” along the seepage direction. When the ini- tial velocity is greater than 0. 03 mm / s,the velocity peak decreases along the direction of seepage. At low-pressure gra- dient condition,there is a nonlinear relationship between the velocity peak and the pressure gradient in the pore frac- ture structure,while the steady seepage value increases linearly with the increase of the pressure gradient. The results provide a new idea for the study of influencing factors of seepage in future research.