Abstract: Nawenmuren community is located in the downstream of auxiliary dam of Ni'erji Reservoir, belonging to the second terrace of right bank of Nenjiang River. The reservoir start impounding in 2005,in recent years the flooding phenomenon, including ground moisture, building cracking, and vegetable cellar ponding had appeared in some part of the fields, making some influence on the inhabitants' living. It has a special groundwater motion law as a result of the existence of a thicker clay formation under the ground. In recent years there is a certain research on this aspect; however the relative information is far beyond enough. It has been found that some flooding has presented in the downstream of the right auxiliary dam, however it is still not clear that whether or not the reservoir caused the flooding. The discussion of this project can offer some reference functions to the similar engineering.