Abstract: The research on the engineering properties of the deep overburden layer is one of the long-term problems in the field of geotechnical engineering investigation. The overburden layer in the dam area of Wudongde Hydropower Station on Jinsha River is deep, and it has complex causes and uneven material composition and structure, which make it difficult to study on the mechanical characteristics, physical and water-physical properties. High cofferdam and deep foundation pit stability problems are serious. In order to determine the engineering properties of the overburden layer and propose the physical and mechanical parameters required for engineering design, some field tests and laboratory tests have been done, such as dynamic penetration test, lateral pressure test, pumping test, sonic wave test, borehole digital TV, routine soil test and simulated gradation sample The engineering problems of the deep overburden layer were solved by conducting comparison and discussion, a reliable basis for the engineering design of high cofferdam and deep foundation pit of Wudongde Hydropower Station was provided. Those methods can be used for similar engineering projects.