The multiscale modeling method is newly introduced to the research on cable anchorage systems for self-anchored suspension bridges with steel box girders to improve the reliability of the conventional modeling methods. Two kinds of boundary conditions (BCs), the hard BCs and flexible BCs, are defined and illustrated. The strategy of the modeling method of the cable anchorage system for multiscale analysis is then introduced. Based on the proposed strategy, a multiscale model of the cable anchorage system is developed for the Taohuayu Bridge, which is the largest self-anchored suspension bridge in the world. For comparison, a scale model test is carried out, and two elaborate finite-element (FE) models, including a traditional scale model and a full-scale model, are established according to the traditional scale modeling method and full-scale modeling method. For further validation, a full-scale whole-bridge elaborate FE model is established, determined as the full-scale G model. In the test, a complex stress distribution of the anchor structure is newly observed. Intensive comparison study of various models demonstrates that the fuzzy region exists in the test model, scale model, and full-scale model, caused by the use of the assumption of hard BCs and the Saint-Venant principle. The fuzzy region cannot be quantitatively determined, leading to unreliable analysis results and a large amount of trial-and-error work. In the multiscale model, the complex BCs of the cable anchorage system are accurately simulated by the flexible BCs, and the influence of the fuzzy region is eliminated. The results of the multiscale model matches well with the full-scale G model. It is concluded that the multiscale modeling method is the most suitable modeling method to simulate the mechanical behaviors of the cable anchorage system of self-anchored bridges with steel box girders, reliably and efficiently. (C) 2014 American Society of Civil Engineers.