Aimed at the issue of modeling end milling process systems, this paper proposes a two-component dynamic model for assembly. The coordinate systems are established, and the receptance of the substructures and combination unit are defined. A complex frequency-dependent stiffness matrix that contains linear stiffness, rotation stiffness and damping are adopted to describe the dynamical model of the combination unit. Receptance coupling substructure analysis is employed to predict the dynamics of the whole assembly. Based on the genetic algorithm, the value of stiffness and damping are identified. A case study proves that the proposed method has good precision to identify the parameters.