Based on field investigation and data collection, a one-dimensional river network water environmental mathematical model for the west bank of the Wangyu River was established using the MIKE11 software. Total pollutant load control calculation and diversion backwater condition analysis were carried out. This study shows how to guarantee the quality standards of the water flowing from the Wangyu River into Taihu Lake during the water diversion period through study of the diversion backwater conditions, when the total pollutant load control on the west bank of the Wangyu River does not meet the standards. The results are as follows: (1)Total pollutant load control cannot be implemented on the west bank of the Wangyu River in the near future. (2)When the water head is lower than the control level, water diversion in the Wangyu River should be conducted; when the water head is higher than the control level, drainage should be conducted on the west bank. (3)In Scheme 1, drainage is required on the west bank after water diversion of the Wangyu River from the Yangtze River for 19 days; in Scheme 2, drainage is required on the west bank after water diversion of the Wangyu River from the Yangtze River for 24 days; in Scheme 3, drainage is required on the west bank after water diversion of the Wangyu River from the Yangtze River for 10 days; and in Scheme 4, drainage is required on the west bank after water diversion of the Wangyu River from the Yangtze River for 15 days.