This paper simulates the characteristics of 3D U-style 180毅bend flow in an open channel using software Fluent with k-棕turbulence model and VOF model, to solve the Navier-Stokes equations. The comparison between the numerical simulation result of water depth and experimental data proves that the numerical simulation can effectively forecast the variation range of both water depth and transverse slope of water surface. Furthermore,horizontal flow fields in different water depths and distribution of circular current in typical sections are analyzed.