Abstract: In order to analyze the strength and deformation characteristics of dam rockfill materials under different confining pressures, the stress-strain characteristics, nonlinear shear strength index and dilatancy of dam rockfill materials under different confining pressures are analyzed by using the large-scale triaxial compression test machine. The applicability of Rowe dilatancy equation to the dilatancy deformation characteristics of dam rockfill materials is discussed, and the deformation and failure mechanism is revealed. The test results show that the stress-strain curve of rockfill material under low confining pressure shows a softening trend, while it shows hardening characteristics under medium and high confining pressure. The nonlinear shear strength index decreases with the increase of confining pressure. Under the low confining pressure, the rockfill material of the dam is first sheared and then expanded, and the shear contraction occurs under the medium and high confining pressure, and the larger the confining pressure, the more obvious the shear contraction characteristics. The Rowe dilatancy equation can be applied to characterize the dilatancy deformation characteristics of dam rockfill materials. Particle breakage caused by high confining pressure is an important factor affecting the deformation and failure of rockfill materials. The larger the particle breakage rate is, the smaller the dilatancy rate is.