Large-diameter monopile is taken as the research object to analyze the deformation behavior of pile, soil and rock, and the stiffness of pile foundation under seismic loads. A nonlinear viscoelastic constitutive model of soil and a damage model of rock mass are introduced to describe the stiffness degradation characteristics of soil and rock media around piles in the finite element-infinite element coupled numerical simulation. The numerical simulation results show that the dynamic responses of large-diameter rock-socketed pile, such as displacement and acceleration, the nonlinear hysteresis characteristics of soil and the damage degree of rock are mainly affected by the depth of rock-socketed pile, the degree of rock weathering and seismic intensity, and should be deeply analyzed in the design.