For steel cable-stayed bridges which have been operating for many years, their static and dynamic parameters have been being changed because of corrosion and overloading. Therefore, an adjustable numerical model, describing and orienting all the various phases of the safety status of bridges, is needed for a theoretical guide of daily maintenance or periodical repair for them. In order to build such a model reflecting the different phases of working conditions of a bridge, a link between the model and the present condition of the targeted bridge should be erected by periodical field inspections for the structure. In this paper, backed on a practical engineering example, the Shengli cable-stayed bridge of Dongying, a finite element model (FEM) based on the periodical field inspection data was proposed, which could possess a strategy modified correspondingly according to parts or all of the results in the field inspections. Specifically, for the initial FEM, three important issues in the modeling of such a complicated bridge, such as simulation of boundary conditions, equivalence of orthotropic steel deck, and implementation of accurate cable tensions, were firstly studied. Then, the initial finite element model built was modified in terms of the optimization principle by minimizing the difference between the static deflections resulting from the field inspection and those calculated by the FEM before being modified. Lastly, dynamic results from the field inspection were compared with those from the optimized FEM to justify feasibility and reasonability of the developed three-dimension FEM which could reflect one or some certain properties of the structure we were emphatically paying attention to. This model-building and model-modifying method for the baseline FEM of the Shengli cable-stayed bridge also provided reference for the similar existing cable-stayed bridges.