Abstract: During the process of hydropower development in China, it is often encountered to use deep deposits or overburden as dam foundation. The causes and compositions of deposits are complex, and their physical and mechanical properties will affect the excavation and utilization scheme of dam foundation. The utilizability of the foundation of the ancient channel deposits on the right bank of Dashixia is studied. The in-situ structural and wetting mechanical properties of the sand gravel and block gravel soil under natural conditions are tested and compared by the pressuremeter tests. On this basis, the mechanical parameters of the deposits are inverted according to the results of the pressuremeter tests, and the calculated values of the mechanical parameters are comprehensively determined with the load test results. Furthermore, the excavation and utilization scheme of the ancient river channel deposits is discussed. The results show that the parameters such as the pressure modulus of the sand gravel layer and the block gravel layer after wetting have a decreasing trend compared with those under the dry condition. After wetting, the cementation state of the deposit body cannot be completely destroyed, and it has high deformation resistance. The modulus coefficient of the accumulated body after wetting is much higher than that of the dam filling sand and gravel. The preservation of the ancient river channel deposits as the foundation of the extra-high dam is beneficial to the deformation control and structural safety of the extra-high dams, and saves the investment and construction period.