Abstract: Water conservancy security in Nanhu mining subsidence land refers to the conservation of lake landscape and downhole production security in Tangshan Mine.According to the geological and mining conditions，the development level of mining-induced fissure is figured out to find the possibility of surface water conduction by the fissure.In addition，the influence of the local caving of steep outcrops on the surface water is analyzed.Besides，it conducts the correlation analysis of water quality between the surface water and the ground water after monitoring the variation of water level.And the variation relationship between downhole water inflow and surface water is also analyzed.The study reveals that there is an alluvium water-resisting layer of about 40~50 m in thickness under Nanhu water storage area，which is composed of clay and sandy clay.With better water resistance，it can prevent the water infiltration in water storage area.What is more，the mining-induced fissure will not extend to the alluvium so that the water resistance will not affected，thus mining-induced fissure and local caving caused by mining will not make surface water sink directly into the down hole.And the correlation analysis among the level，quality and amount of water shows that the surface water has no direct hydraulic connection with water inflow and therefore it is feasible to conserve water in Nanhu mining subsidence lands.

Key words: Mining subsidence, Water conservancy security, Hydraulic connection, Aquiclude