Abstract: The development of fractures and pores in coal is the main factor affecting the seepage of water injection. With the advance of the working face, the mining stress will cause the change of coal seam pore fracture structure. In order to explore the change law of pore and fracture in coal during mining, based on triaxial compression experiment, volume deformation is used to characterize the evolution process of pore volume change with stress loading. Fluent custom function （UDF） is applied to program the relationship between pore volume change with loading time. Taking mining time and water injection time as axes, the effect of mining dynamic stress on seepage field of coal seam water injection is analyzed by numerical simulation. By comparing the changes of seepage pressure, seepage velocity and water injection in the seepage field near the borehole in different stress loading stages with the same time increment, the results show that under the same time increment condition, the water pressure around the borehole increases successively, the water content around the borehole increases successively, and the water injection wetting range expands successively in the compaction stage, volume expansion stage, deformation and failure stage. It can be seen that mining stress has an important influence on water injection seepage.