Abstract: By analyzing the water-filled factors of Pingshuo No.3 Coal Mine, roof water inrush from carboniferous-permian sandstone is considered to be the most hidden trouble during mining No.9 coal seam. Meteoric water, surface runoff and water from Dashagou rechargeing the lower aquifer and into mine are also the nonnegligible factors. Also, falling safety of coal seam roof water is analyzed and evaluated by using the result of the height of the water flowing fractured zone, which provides basis for decision making in preventing and control water disaster.