Abstract: For the earth core rockfill dam, the coordination of the strength and deformation of the dam is a key issue that restricts the dam construction. The deformation of the gravelly soil core materials is large, which leads to the transfer of the load to the coarse grain of the dam shell with relatively small deformation, resulting in arching effect, which can lead to hydraulic fracturing and destroy the seepage control system of the dam. The gravel soil core materials of high earth core rockfill dam, containing coarse particles with larger particle size and a large amount of clay, have small permeability coefficient and consolidation of saturated drainage problems, resulting in that strength and deformation are difficult to be accurately measured in large-scale tests. Using sand core to increase saturated drainage channel and accelerate sample saturation and consolidation can effectively solve this problem. For the gravel soil core materials, a series of triaxial shear tests and plane strain tests are carried out with diameters of 500, 300, 150, 100 mm. The shear rate, sample size, maximum particle size, stress and other factors are discussed on the strength and the deformation of the deformation parameters, and the real strength of gravel soil core materials is obtained.