The steel structure of Hefei Xinqiao International Airport Terminal was taken as a background of this article. The large-span frame is a typical frame of the structure. The curved box-girders are the critical parts of the whole frame. This paper focused on the mechanical properties of the curved girders, as well as the influence on box-columns connected with them. Stability problem is a key problem in the steel structure design, and effective length factor is a way to reflect the stability problem in code for design. In this paper, the whole model of the airport terminal was established to conduct eigenvalue buckling analysis to obtain effective length factors of the box-columns connected to the curved box-girder. In the finite model, a unified axial force was applied on the end of the box-column, and the elements of the box-columns and the adjacent members were refined. Then the effective length factors were derived through the buckling models. In this paper, the curved box-girders of Hefei airport building were studied using finite element software ANSYS. The local model of the curved box-girders were set up to study the mechanical properties of the curved girders including the ultimate capacity analysis. Parametric analysis of the girders was carried out, and the results could be used to guide the design. The results show that finite element method is a convenient way of calculating effective length factors for members with complex boundary conditions, and analysis of local models provides reasonable suggestions for design.