Aiming at the problem of the pollution to effluent discharging river from sewage treatment plant, this paper proposed an idea that taking advantage of the conditions of river itself and surroundings of river to purify the effluent from sewage treatment plant without affecting the original functions of the river. And the purification effects of the demonstration project renovating on the effluent discharging river from sewage treatment plant in Taicang, Suzhou City was studied. The results show that the enhanced purification system set inside the river could further remove the pollutants from the effluent effectively, and the removal efficiency of organic matter, TN, TP were more than 20％, reducing the pollution of the sewage treatment plant on the receiving river.