Abstract: For researching bend flows,as well as expanding the application of the Lattice Boltzmann Method (LBM) in the water conservancy field,a 3D multi-relaxation times LBM model,which includes free surface simulation,curved boundary treatment and turbulence models solving,was established.U-type bend flows under different flow rates were simulated,and the distributions of water level,maximum depth-averaged velocities and turbulent kinetic energy were obtained.Both the theoretical analysis and the simulation result indicate that the model in the paper can adequately simulate 3D bend flows.