The fluctuating backwater area under the dam of Beijiang Baishiyao water conservancy is an important navigation obstacle shoal to the middle of North River. Before waterway regulation engineering, the depth of waterway is shallow, so ships must reduce the load or delay sailing. Ship jam often occurs and water depth keeps only between 0.8~1.0 m. Even suspension of shipping occurs from time to time, so waterway regulation engineering is necessary. In order to achieve Class-III channels, this paper analyzes the characters of the evolution of these shoals, develops a river work model, takes full advantage of the regulating structures and makes the best use of the general trend, and takes appropriate measures to analyze the two waterway regulation schemes of Class - III channels, then proposes regulation scheme. According to the analysis result, it is feasible for the reach to achieve the waterway scale of 2.5 m×60 m.