Based on the project of four-level waterway construction from the Lancang River 244 mere Stone to Lincang Harbor and depending on the beaches from Xigua to Mengsong,this article illustrates the characteristics of waterway and hydrology.Because there are not enough waterway length and depth in the rivers and shoal groups of the canyon,single beach regulation causes the fall of river level in the upper shoals and the speed of the river and gradient slope change in a bad way,leading to new navigation obstacles.Analyzing the evolution rules of rapids and riverbeds and combining with the situations in the history,it researches the characteristics of the single shoal and shoal groups navigation obstacle,adopts the method of enlarging water-carrying section in the way of cleaning the rocks and solves the problem of single shoal navigation length and depth.Meanwhile,it adopts the combination of damming the river step by step and dredging in different sections to deal with the fall of the water level because of shoals and rapids connections.Therefore,it is concluded that the combination of cleaning rocks and damning can solve the puzzle of rapids connections and influences