Tianshan Pumping Station takes water from the Yellow River. A three-dimensional (3D) mathematical model of turbulence flow patterns in the forebay and suction sump was developed and a 3D turbulent flow simulation technique applied to numerical calculation of the flow pattern characteristics in both the original and rebuilt forebays of the pumping station. The numerical simulation results were analyzed and contrasted. The results showed that, with technical improvement, surface backflow was avoided, and bottom velocity in the forebay was increased while bottom velocity in the suction sump was unchanged. Because of this, there was no sediment deposition in the bottom of the forebay, and flow velocities in the forebay and suction sump were more evenly distributed.