Abstract: More than 80% of mine water inrush accidents are related to faults in China, most of which are non-conducting faults under primitive geological conditions that cause water inrush under the influence of mining. Structural defect and mining effect of faults are two important causes of fault water inrush. In order to deeply explore the fault water inrush mechanism, the in-situ water pressure test and hydraulic pressure dynamic monitoring of the deep roadway fault are carried out from the characteristics of fault itself impermeability and its susceptibility to mining effect. The impermeability of the fault is studied and real-time safety under the influence of mining conditions was monitored. The results show that: comparing the pressure test results of the normal bottom plate, both the fault and the normal bottom plate are found to have the process of flow mutation, flow increment and flow surge; the impermeability of the fault and normal bottom plate is 0.64 MPa/m, 2.03 MPa/m, respectively, and the impermeability of the unit thickness fault is obviously weaker than that of the normal bottom plate; during the mining process, the internal seepage field of the branch fault has changed, but did not cause fault-activated water inrush.