The experimental study is carried out for the flow channel of a large-scale circulation pump, the flow pattern, water velocity and flow rotating strength is focused on. It is found that there exists a strong vortex in the lower part of the absorbing well and a spiral flow in the suction pipe, which could be the primary cause to affect the inlet of pump. The safety and reliability measures for the pump is thereafter suggested, the breast wall is used in the water-absorbing room, the elevation of the breast wall is optimized and given.