The movement law of overburden strata and the growth of water flowing fractures in overburden strata during mining advanced process for 31401 fully mechanized working-face of Bulianta coal mine were simulated using rock failure process analysis software(RFPA2D).The result showed that in the advance process of the working-face,the third water stratum together with it’s upside mudstone and bottom sandstone strata,can compose the water resisting compound key stratum,which is capable of preserving the first and second water stratum and preventing the disappearance of groundwater resources.