Abstract: Aiming at water seepage problem of roof and floor sandstone of No.3 coal layer in Tangkou Coal Mine, this study focuses on the pore structure of the sandstone through the optical, electron microscope scanning analysis test experiment to explore the composition of microporous sandstone, and analyzes micropore seepage of sandstone by means of numerical simulation at the same time. Combining with water seepage information, the stu dy expounds the water seepage process. The results show that: seepage flow of solid sandstone is mainly microporous seepage, and pore water pressure and throat diameter are the main factors affecting seepage flow;the water seepage process could be divided into three stages: matrix softening stage, matrix erosion stage and stage of throat diameter enlargement and seepage increase.