Locating in the confluence of Qian river and Yu river, and in the fluctuating backwater area of Changzhou hydro-junction as well, Yanglantan beach is characterized by trong currents, chaotic flow, large crossflow and poor navigation conditions. It is very difficult to increase the channel dimensions from class Ⅳ to classⅡ,which would be studied mainly by the physical model. Based on the hydraulic characteristics, four improvement ideas are compared such as channel widening, improvement engineering at the junction in Qian river, excavating at the left branch or in the middle channel of Dasha for diversion. The scheme of excavating out of channel for diversion is advanced. The analysis of measured regulation effect shows that the value and location of large flow field which is predicted by the model test are consistent with the original, and the the channel conditions have been improved significantly by the engineering.