On the basis of historical evolution analysis，this paper focuses on the change，cause and effect mechanism of the the inlet section of the northern branch of the Yangtze River in recent years. This paper simulates and studies the effect of planning and remediation scheme of the inlet section by the mathematical model. The results show that，affected by the changes of runoff and sediment from the upper reaches and the implementation of the surrounding remediation projects，the sandbar in the inlet section of the northern branch of the Yangtze River has experienced the development and change of tongue-shaped sand body → Chongtou shoal → Chongtou sand，and the inflow conditions of the northern branch deteriorates. The deep troughs on both sides of the sand body show an alternating trend of “ten years east of river and ten years west of river”. The current main trough is located on the Chongming side，and its direction and the main flow of the south branch reaches an intersection angle of 105°，and the main flow path is extremely curved.Under the circumstance that most of the planned renovation projects in the middle and lower sections of the North Branch are implemented，the treatment of the entrance section becomes the key to the rise and fall of the North Branch. After the implementation of the planned dredging project for the entrance section of the North Branch，the flow path of the entrance section returns，and the diversion ratio of the North Branch increases 0.1%，the implementation of the project is conducive to the stability of the river and achieves the purpose of treatment.