With the development of social economy, the contradiction between water supply and water demand is increasing. In order to alleviate this contradiction, an underground dam is proposed to be constructed in the downstream of one river for intercepting subsurface flow and increasing conjuctive utilization of surface water and groundwater. According to the hydrogeological condition of the downstream of one river, a groundwater flow numerical model through Visual Modflow was built to analyze the regulation and storage of groundwater for underground reservoir. The conclusions are as follows: the underground reservoir of a River has great potential for exploitation; the water regulation by storage of wet, normal, dry and special dry years is 23.928 million m3, 20.565 million m3, 17.43 million m3 and 10.128 million m3, respectively, and after the construction of underground reservoir, river has a great potential for development; the extraction scheme of 36 wells with a flow rate of 0.015 m3/s for the whole year is a more suitable scheme plan.