Abstract: Due to changes in upstream conditions since 1930s， the left branch of Baguazhou inlet has been gradually evolving from the main river branch to the subsidiary channel. In recent years， since the variation of discharge and sediment concentration， the rate of decay of the left branch has accelerated again， with diversion ratios as low as 12% observed repeatedly. For this reason， engineering treatments are urgently required to curb the recessionary trend of the left branch. According to the engineering measures， a physical model and MIKE21 hydrodynamic numerical model are used to simulate the water level， flow rate， and diversion ratio of the Baguazhou inlet. The improvement effects on the diversion ratio of a diversion dam， cutting of the beach， dredging， several separate schemes and combined schemes are mainly analyzed. The analysis results show that the diversion effect of the diversion dam is quite good and combined regulation works can increase the left branch diversion ratio by as much as 4.76%. By comparison with the physical model， it provides a theoretical basis for the implementation of the regulation works and gives suggestions for further improvement of the regulation works.