Abstract: The thin-walled steel pipe pile bracket is a temporary support structure commonly used in the construction of large-span aqueducts and other projects. Because its slenderness ratio is relatively large, the buckling instability problem is more prominent. Therefore, the accurate calculation of its structural safety factor is the key in the design. In order to study the effect of stress concentration on buckling instability of steel pipe pile bracket, combined with a large-scale aqueduct project, the beam elements and shell elements are used to establish steel pipe pile bracket models, and the buckling critical load of steel pipe pile bracket under different diameter-thickness ratios and bracket heights are compared and analyzed through the finite element software ABAQUS. The results show that there are obvious differences in the buckling instability modes of steel pipe pile bracket under different models. Because the beam element cannot reflect the local stress characteristics well, the obtained structural safety factor is relatively important, and the calculation result is dangerous. For the thin-walled steel pipe pile bracket, the relative difference of buckling critical loads under the two models is positively correlated with diameter-thickness ratio and initial imperfection. When diameter-thickness ratio is greater than 20, the relative difference between the two is greater than 11.4%. In actual engineering, we recommend using shell element for stability checking.