[Purposes] This paper explored the influence pattern of auxiliary pier position on the mechanical performance of long-span cable-stayed bridges with hybrid and composite girders incorporating PK section by establishing multiple finite element models with different numbers and positions of auxiliary piers and comparing the static and dynamic calculation results, and a cable-stayed bridge (with a main span of 530 m) with hybrid and composite girders incorporating PK section was used as the engineering background. [Methods] Finite element models of the cable-stayed bridge with double auxiliary piers, a single auxiliary pier, and no auxiliary pier were established. The structural internal force, deformation, and natural vibration period and frequency of the three models under vehicle load during the operation stage were compared. [Findings] Compared to the model without auxiliary piers, the setting of double auxiliary piers and single auxiliary pier can reduce the maximum mid-span deflection of the main girder, the maximum displacement of the tower top, and the first-order natural vibration period by 45.3%, 62.9%, and 26.2%, as well as 42.1%, 48.6%, and 17.2%, respectively. The auxiliary pier can significantly improve the static and dynamic performance of the structure, with a single auxiliary pier being an economically feasible scheme. In addition, five finite element models with a single auxiliary pier at different positions (59.2, 73.6, 95.2, 109.6, and 131.2 m away from the center of the main tower, respectively) were established to compare their structural responses under vehicle load during the operation stage. Compared with Scheme 1 (with the auxiliary pier located at 59.2 m away from the center of the main tower), Scheme 5 (with the auxiliary pier located at 131.2 m away from the center of the main tower) can cause reductions in the maximum mid-span deflection of the main girder, the maximum displacement of the tower top, and the first-order natural vibration period by 25.6%, 19.1%, and 1.8%, respectively. [Conclusions] By considering the safety of cantilever construction, Scheme 5 is established as the final design scheme.