Abstract: How to implement mining with water protection is a major research topic in ecologically fragile areas. Hydrogeology and engineering geology conditions exploration test and division index study are an important foundation and prerequisite for the implementation of water protected mining. This paper takes a typical mine of northern Shaanxi as an example. It is based on the exploration test. It includes the results of water pressure test before and after mining,indoor simulation of mining overburden rock deformation and failure process of permeability variation test. The results show that coal mining has a different impact on overlying rock mass permeability. The permeability of siltstone and mudstone is lesser and it can be used as a weak aquifuge. After mining,the bedrock permeability of the overall mobile belt appears varying degree of increase. The permeability coefficient increases about one order of magnitude. The red clay permeability variation is not obvious. Red clay can be used as key aquifuge before mining. According to water resources leakage,recharge and water level changes,the ecological fragile area is divided into four zones,i.e.,not influenced zone,zone of light water leakage,zone of normal water leakage and zone of serious water leakage. On the basis of the principle of water balance,the condition partition index of the four types calculation formula is derived. The application example is given.