Lots of mine water pours out during period of mining to ensure the safe mining. However, it is inevitable to decrease the groundwater level around the mining area and even to influence the water supply safety of the constructed groundwater source fields. As a result, the conflict between water supply and mining drainage happens. Therefore, in this paper, a case study of Xulou iron ore in Huaibei City was taken to evaluate the effects of mine drainage on the urban water supply in safety. Besides, uncertainty of the coefiqcient of leakage was also analyzed in quantity. The study results show that the maximum additional drawdown of water level is only 0.0244m, which is only 0.41% of the designed drawdown. Therefore, there is a little effect on the water supply safety.