Abstract: In order to rationally determine a pre-drainage safety water level of the aquifer in the roof above the coal mining face before the mining operation, a met hod to determine the safety water level was provided based on the water drainage capacity of the coal miming face.a numerical simulation method was applied to establ ish a 3D geological model of the rock strata in the mining area according to the borehole information. With the data of the water pumping, water drainage and water inje ction test, the watery division and parameter rate were conducted on the initial flow field of the water drainage target aquifer. With the establishment on the pre-drainag e underground water flow field generalized model before the drainage operation of the coal mining face, the final water level variation tendency of the aquifer was calcul ated and analyzed under the condition of different water drainage intensity. According to the final position water level under the different water drainage intensity, the m ax water inflow during the production period of the coal miming face was simulated and calculated and the method to determine the water pre-drainage safety water lev el before the mining operation of the coal mining face was summarized and formed according to the water drainage capacity. The site application results showed that th e calculation value of the method and the face actual inflow were close and could be the judgment criteria to the pre-drainage safety water level of the roof aquifer befor e the mining operation of the coal miming face.