Earth-rock cofferdam is a common cofferdam support method，and its stability and impermeability effect have an important impact on the safety of water conservancy projects.Taking the upstream and downstream horizontal earth-rock cofferdam project of Yanzhou Hub phase I in Changde City as the research object，in view of the three aspects of rock mass fragmentation and fragmentation，soft interlayer and landslide in the area，a multi-layer interactive protection construction scheme to cope with this working condition is innovatively designed，and the stability performance of the slope and rock protection of the earth-rock cofferdam is further analyzed and studied.Firstly，the construction difficulties caused by the hydrogeological conditions of the Yanzhou Hub cofferdam project are introduced in detail.Then，the cofferdam structure and impermeability design are studied by theoretical analysis.Finally，the stability of the earth-rock cofferdam is studied by numerical analysis.The engineering construction results show that the design scheme provided in this paper can well meet the requirements of cofferdam deformation control under harsh geological conditions in this area，which can provide reference for the design and construction of similar projects.