Abstract: This paper takes the South Jiangsu Canal-Li River-Wangyu River Interchange Channel as the research object, based on the verification of the overall one-dimensional river network mathematical model of Jiangsu Taihu area and the local physical model of the South Jiangsu Canal-Li River-Wangyu River intersection, a two-dimensional mathematical model of intersection is constructed. Based on the “16.7” exceeding-historical flood data, the combination of the physical model and the calculation of current intersection angle, the characteristics of the Li River diversion ratio under the conditions of the South Jiangsu Canal-Li River interchange angle are further simulated and multi-factor impact analyses are carried out. The results show that the junction of the South Jiangsu Canal- Li River -Wangyu River is different from the “Y” type or the slanting junction, and the water diversion ratio of the Li River is mainly due to the water level difference between the Wangyu River and the South Jiangsu Canal-Wangyu River, which has little relationship with the discharge flow of the South Jiangsu Canal. The influence of the intersection of the South Jiangsu Canal and the Li River on the diversion ratio of the Li River is not significant. It is mainly because the mouth recirculation zone shrinks the effective over-water width of the tributary, resulting in the actual width of the inlet smaller than the tributary width.