Abstract: In order to predict mine inflow accurately,protect water resources and ensure the ground water safety of well mining,on the basis of generalizing the hydro-g eologic structure model of the Datong Mining Area,the three-dimensional numerical simulation model of transient flow had been established. This paper took monthly produ ction schedule of coal mining face in Tashan filed as unit,the normal and the max ground water inflow of No.8214 and No. 8216 working face when ground water level in dif ferent periods was down to the bottom of coal seam No.5 respectively were stimulated. The No. 8214 and No. 8216 coal mining face,normal mine inflow of were 1 224 and 1 392 m3/ d respectively,and the maximum mine inflow were 1 272 and 1 440 m3/ d respectively. The caculation results were more accurate when the method combined wit h the mine inflow and monthly production schedule of coal mining face was used.