In order to build the multibody system dynamic model of the tower crane, the absolute nodal coordinate formulation cable element is used to model the steel wire rope in the hoisting system. As a characteristic of the absolute nodal coordinate formulation, the mass matrix is constant while the tangential stiffness matrix is varying. The whole process of the rope motion is divided into several subdomains. The first order Tylor expansion is applied on the dynamic equation of the rope within each subdomain. Therefore, the order reduction based on modal truncation can be performed. The kinetic constraint is used to integrate the structural vibration equation and the large-deformation equation of the steel wire rope to form the multibody system dynamic equation of the entire tower crane system. The local linearization formulation of the constraint equation is also given. Numerical results demonstrate that the multibody system dynamic modeling and order reduction method proposed in this investigation can effectively reduce the size of the problem and improve the simulation efficiency without losing accuracy.