In China, being a big coal mining country, subsidence caused by coal mining has become a serious artificial geological disaster. Coal mining subsidence not only changes physiognomy morphological character around the mining areas but also makes abundant cultivated land, garden plot, holt, traffic land and construction land change to water area. Coal mining subsidence has become a major obstacle to the sustainable development of society, economy and environment in mining area. Imaginal, intuitive and accurate simulation of the submerged area of confirmed water level in the different periods and with different subsidence scale is the foundation of governance and reclamation of subsidence area. With Longkou coal mining subsidence area in Shandong Province as case study, on the base of 1: 10000 contour lines and dispersed elevation point data of the research area of five periods gathered by ArcGIS software, which were 1978, 1984, 1996, 2000 and 2004, this paper has completed contour line’s density interpolation, then the digital elevation model (DEM) of uniform grid with 1* 1 m² can be gained from triangulation by linear interpolation. This paper considers the DEM data of 1978 before subsidence as standard elevation, and calculates the coal mining subsidence region and area through the difference operation between DEM data of the other later periods and the standard elevation. Obviously, when z value of a certain place is less than zero, which represents elevation, the place has become subsidence area. According to the data observed by water department during 48 years, the author figures out the hydrographic feature values of different frequency year flood season in coal mining subsidence area. Then the water submerged area of confirmed water level in coal mining subsidence district were calculated by "non-fountainhead flood" analysis method and verified by contemporaneous result of remote sensing image interpretation. The main conclusions are as follows: firstly, the analysis method used in the paper is very dependable, whose maximum relative error and minimum relative error are 5.76% and 2.83%, respectively. Secondly, the general trend of the change of the water submerged area is that it will be enlarge with the enlargement of subsidence area. In addition, the increasing amount of the water submerged area is less than that of subsidence area. In the future, subsidence area in the continent will be joined with that in ocean bottom. If people can’t prevent and what treat the trend effectively, seawater intrusion will occur widely in subsidence area, and along with it is the irreversible ecological change in the land. Lastly, the primary factor influencing on calculation precision is DEM data.