Due to the sediment deposition occurring in front inflows of the straight-edge forebay of large pumping station, where its water is taken from the river with high content of sand, the adjustment ability of the forebay is usually reduced and the operation efficiency of the pumping station becomes low. To solve this problem, a prototype 3D model of the forebay structure is established using the ICEM CFD software, with its flow regime being modelled and analyzed by using Standard k-εturbulence model in the FLUENT software. Moreover, two optimization measures are proposed for the bad flow regime by incorporating diversion pier or water pressure plate. The findings show that the computed results are consistent with those from site survey, the flow regime in the forebay is in disorder and the sand sedimentation is quite serious. The eight-shaped diversion pier can reduce to some extent the scope of the main re-circulation region, but only serves as allocating of the forebay flow without obvious improvement in its flow filed distribution. On the contrast, the 45°water pressure plate can effectively improve the mainstream effect in the forebay, and the back-flow region on both sides is obviously reduced. The sand sedimentation problem in the forbay is thus solved with the favorable inflow conditions being ensured for the water pump.