Based on the analysis of the data from physical model test and field observation, we study the reason, trend and detrimental effect of the change of river regime on the south channel recently and propose corresponding countermeasures. The results show that: 1) Due to the large-scale water conservancy engineering, an obvious adaptable adjustment of the river regime on the south channel is happening; 2) Without other engineering measures taken, the unfavorable influence due to the river regime’s variation of the south channel will exist for a long time; 3) The unfavorable influence can be controlled if we implement appropriate artificial engineering on Ruifengsha.