Abstract: The present situation of regional rivers and water resources has been exposited based on the historical hydrographic data since last century in the Haihe River Basin, and the necessity of storage for flood resources was discussed. Combined with the breakwater safety programming of Tianjin, China a design scheme to build a artificial lagoonat the Yongdingxin Riveren-trance as an ocean reser voir was presented. Making use of the 3-D hydrodynamic and water quality coupling computation model, water quantity and salinity dynamic process of impounding into the planning ocean reservoir were simulated under different conditions of opening the drainage sluicegate and closing the intake sluicegate. Results show that salinity in the ocean reservoir was higher when the drainage sluicegate was closed;the dilution and permutation course of high salinity water can be promoted by opening the drainage sluicegate;pumping from the ocean reservoir can cause the intermixing phenomenon of reservoir bottom water body and salinity, however the low-salinity freshwater of top and central section in the ocean reser voir can keep stability.