Abstract: In order to effectively predict water flow in goaf at the initial mining period of fully-mechanized top coal caving face,an empirical formula was applied to C alculate the height of the roof falling zone and the height of the water flow zone in fully-mechanized top caving face. According to the borehole information,No. 9 aquifer was located in a water flow zone as determined. Based on the circumstances,a FLAC3Dsoftware was applied to simulate the mining process of fully-mechanized coal C aving face, the distribution law of the roof falling zone and water flow fracture zone occurred by the vertical displacement of the overburden strata was obtained and the i nterconnection between the water flow fracture zone and No. 9 aquifer would be the water sources of the water flow in the goaf of the coal mining face. The results sho wed that before a full mining reached,the water flow fracture zone was arch shape and the water flow in goaf,numerical simulation on the coal mining at 108- -112 m of t he coal mining face and the site mining at 106 m of the coal mining face was fitted. Thus the results verified the numerical simulation could accurately predict the water flow in goaf.