Abstract: In order to analyze the mechanism of the siltation of urban river in Changzhou,this paper uses the method of dimensional analysis and water channel experiment to study the influence of bank slope angle,flow ratio and density Froude number on the scour of the confluence area during the process of tributary river flowing into the mainstream river. In this study,the confluence angle of tributary flume and mainstream flume is set at 90°,and four different bank slope angles（45°,60°,75°,90°）are compared with different flow ratios and density Froude numbers. The results show that the smaller the ratio of flow in tributary to the flow of the main stream,the greater the influence of the bank slope angle on scour depth is. For any given density Froude number,the smaller bank slope angle can lead to the smaller scour depth.According to the two empirical relations obtained by fitting,the influence of the bank slope angle on the height of sediment deposition is more than that on the scour depth,and the density Froude number has the greatest influence on dimensionless scour depth,and the bank slope angle has the greatest influence on the dimensionless sedimentation height.