The regulation of a bifurcated tidal estuary usually can lead to the water diversion ratio to decrease. At present，there is no quantitative assessment of the river regime effect of such diverging ratio reduction. Based on the DOU Guo-ren equation，the correlation is analyzed between the changes in water and sand conditions and river hydraulic geometry relationship of the North Passage since the implementation of the Yangtze estuary deep-water channel regulation project. The results show that：1）The theoretical adjustment range of river hydraulic geometry relation after the project is less than the actual change. The large-scale dredging and the decrease of local sediment concentration are the two important roles in balancing the actual adjustment of river hydraulic geometry relation. 2）At present，the low sediment content environment of the North Passage supports the increase of the average depth in the main trough，but the volume of the main trough still needs to be stabilized by dredging.