Abstract: The problem of water seepage through sandstone micro-fractures in deep well is one of key factors influencing normal production. With the method of single factor sensitivity analysis, this paper is to tell us how to affect the seepage of micro-fractures by roughness, fracture opening, confining pressure and seepage pressure by self-developed micro-fracture triaxial stress seepage mechanism model test system. Simultaneously, numerical simulation is used to study the seepage process of micro-fractures in sandstone, and explain the evolution process of hydraulic fracture under water pressure. The results show that the factors that affect the seepage of micro-fractures from strong to weak are osmotic pressure, roughness, fracture opening and confining pressure; the evolution process of hydraulic fracture propagation under water pressure can be divided into the stress accumulation stage and the stable expansion stage of micro-fractures.