Water conservancy project cofferdam sub-weir and construction method thereof

The invention provides a hydraulic engineering cofferdam sub-weir and a construction method thereof. The hydraulic engineering cofferdam sub-weir comprises a cofferdam body and a heightened sub-weir, the cofferdam body comprises an earth-rock weir and a concrete panel, and the concrete panel is fixedly arranged on the outer surface of one side of the earth-rock weir; the heightened sub-weir comprises membrane cloth, filling soil, color strip cloth, two sets of canvas bags, capping soil, a plurality of reinforcing steel bars, a plurality of filling sand, a hollow elastic pipe support and hydrogel, the cofferdam sub-weir is structurally optimized by actually measuring water level flow data, and the water level flow data of multiple floods of a water conservancy project and multi-year hydrological observation data of a river channel are actually measured, so that the cofferdam sub-weir is constructed. Related engineering design is optimized to achieve the purpose of saving the manufacturing cost, and meanwhile t