Abstract: Based on the development characteristics of Ordovician limestone aquifer and hydro-geological characteristics in Zhaozhuang well field, we combined with the structural characteristics of this area, the combination of coal seam floor rock layer, water inrush coefficient to evaluate the safety of the lower group coal seam mining. The results show that Ordovician limestone aquifer is deep in the west, shallow in the east, weak-strong in the upper part, middling-strong in the lower part; the larger normal fault will make the lower group coal seam contact directly with the middle Ordovician strong water-bearing limestone to increase the water filling property of the coal seam, which has a certain threat to the coal seam mining; 15^# coal seam floor layer combination with weak-hard-weak type will occur soften phenomenon under the action of groundwater to reduce the stability of coal seam floor; in the southern block and the eastern part of the block, the water inrush coefficient is within the range of safe mining, and the danger of water inrush exists in other areas.