Abstract: To release the lower coal seams of Wangpo Well Field being threatened by Ordovician karst water, based on the theoretical basis that there is an aquifer at the top of the ordovician system in North China, using hydrogeological drilling, pumping water testing, salinity logging, water pressure testing, drilling and peep tests and other ways, the water permeability of top strata of Wangpo Well Field Fengfeng formation is analyzed and studied. The results show that the top strata of Fengfeng formation in Wangpo Well Field has a ancient weathering crust with weak water yield property, low permeability, less cracks, which can be considered as a relative aquifer.