According to the actual data from returning land to lake in the Poyanghu Lake Area and by adopting the method of flood simulation, in this paper, the lowered flood stages at the Hukou Gauging Station by returning land to lake and the reduced flood diversion quantity above the quota of 1954-year flood have been analyzed and calculated. In addition, this paper analyzes the flood control and disaster relief situation of the Poyanghu Lake Area after returning land to lake, suggests strengthening construction of flood control projects in Poyanghu Lake Area, and gives a discussion on the variation tendency of river-lake flood relationship after returning land to lake.