In order to predict the influence of the daejeon sewage treatment plant relocation on the water quality, the paper simulated changes in water quality due to the relocation by using EFDC model, 3 dimensional numerical model. The main research results of this study are as follow. When the sewage treatment plant discharge point was moved to the planned relocation site at the downstream of Gapchun, under the same condition, the average load of COD(chemical oxygen demand) was increased by 8.55 kg/d, T-N(total nitrogen) by 7.274 kg/d and T-P(total phosphorus) by 0.077 kg/d, The paper analyzed that the water quality after the relocation of the sewage treatment plant is worse than the water quality before the sewage treatment plant relocation. The T-P treatment efficiency of the sewage treatment plant is at 98.1 %, Therefore, only if the treatment efficiency is higher than 98.3 %, ‘Geumbon G’ water quality target can be reached.