[Objective] Designing a series of measures to bring the floodwater back to the floodplain on the premise of guaranteeing flood control, no destroy to current land use and hydraulic facilities in order to accelerate storing floodwater on the floodplain and make the water resource allocation more reasonable. [Methods] According to the ecological theories, the ecological floodwater storage design was carried out on the base of current river improvement work by image analysis and field investigation. The design core was floodplain water diversion net for a floodplain of Huihe river in Ningwu County of Shanxi Province. [Results] It contains measures such as pool & riffle sequences, chain of ponds and passageways of flood diversion. It can bring the floodwater into the floodplain and store the water under the ground to recover the water storage function on floodplain as far as possible, and to adjust the river discharge and weaken the flood. [Conclusion] Floodplain water diversion net design conforms to the natural law of the river ecosystem. It can give furthest play to ecological benefits on the premise of economic and social development, to protect the ecological water storage function for small rivers, and to recover healthy rivers and watersheds.