Abstract: Based on the morphological characteristics of river-bed of tidal estuaries, a calculation formula for the widening rate of the estuarine regulation line is derived. By use of the morphological coefficients of estuarine river-bed and the relevant data of the north channel of the Yangtze River Estuary, the widening rate of the regulation line of the north deep-water channel of the Yangtze River Estuary is calculated, and the calculation result is in agreement with that of the fixed bed model test.