This paper studies the general hydraulics of the inflow of tributaries to the curved reach by the conceptual model, reveals the variation characteristics of surface geometry and surface slope and distribution law of 3D-velocity,hydrodynamic axis and bed shear stress under various confluence angles and various discharge ratios,presents the condition in which the recirculation zone could appear near the concave bank downstream the junction,and gives the quantitative relationship between the scale of recirculation zone and confluence angle & discharge ratio. This paper also analyzes the bed load movement and riverbed erosion and deposition site at the junction. It lays a good foundation for further study on this kind of rivers.