Relying on an expressway project in Jiaxing of Zhejiang, through the establishment of the rod system model of Y-shaped pier of the substructure and the finite element solid model, the stress analysis and comparison under the action of eccentric load are carried out. Combined with the strut-and-tie theory, it is revealed that the rod system model is difficult to reflect the real stress situation of the structure when analyzing the Y-shaped pier. The results of the solid model analysis are more reasonable. On this basis, the optimal design criteria for the stress of Y-shaped pier are further proposed, and the optimal design is carried out accordingly, which provides a reference for the design and research of the substructure of the similar bridges in the future.