Abstract: Considering the continuity conditions and boundary conditions of the pile and soil, the vertical dynamic displacement of the soil was obtained based on continuous mechanics model, and established the vertical dynamic differential equations of the embedded part and exposed part of the pile. The vertical vibration of partially embedded single pile was solved by considering the continuity conditions and boundary conditions of the embedded part and exposed part of the pile, and the influence of the length of embedment of pile and the pile-soil modulus ratio on complex stiffness at pile head was investigated with numerical example. Through the discussion of parameters, it was concluded that the resonance of partially embedded single pile will occur under harmonic dynamic load, and the length of embedment of pile and the pile-soil modulus ratio have great effect on the complex stiffness of the pile at pile head, the fluctuation of the curves of complex stiffness of the pile at pile head varying with frequency will more seriously when the length of exposed part of the pile is longer