Abstract: It proposed a form-finding method for railway catenary based on the dynamic theory, which is described by absolute nodal coordinate formulation (ANCF) in the flexible multibody dynamics theory. In the context of nonlinear problems, the catenary is modeled using ANCF cable element based on the flexible multibody system formulation and variable-length element theory. According to the static equilibrium conditions, the dynamic model is degraded and the form-finding model of tensioning structure is built. Meanwhile, considering the pre-sag design requirement of the contact wire, the models of contact wire and steady arm are separated out and solved using the form-finding model of tensioning structure. The force of droppers is updated for computing the equilibrium of droppers and messenger wire system according to the form-finding model. The equilibrium of railway catenary is determined. Three examples are adopted for verifying the proposed method, the results show that the proposed method can compute the equilibrium configuration of railway catenary exactly and the maximum relative error is less than 2%, which satisfies the engineering requirement.