Abstract: The static buckling load is an important indicator for evaluating the structural stability and basic load-bearing capacity of nuclear fuel assembly spacer grids. However, the buckling characteristics of spacer grids are influenced by various uncertainties, including material properties, geometric parameters, and assembly precision. These factors make it difficult to quantify the critical drivers of buckling behavior, posing significant challenges to design optimization. Therefore, this study investigates the buckling behavior assessment and sensitivity analysis of spacer grids. First, a numerical analysis model was established and validated against experimental buckling data. Subsequently, a surrogate model for buckling response was developed based on multi-output gaussian processes. The Sobol global sensitivity analysis method was then employed to quantify the effects of material, geometry, clamping force, and friction parameters on buckling characteristics. Based on the sensitivity results, the key influencing factors and their contributions were identified. The results indicate that the friction coefficient, strap thickness, clamping force, and Young’s modulus of Zr4 are the main factors affecting the buckling load, with a cumulative sensitivity index reaching 99.27%. The buckling displacement is primarily determined by the friction coefficient and clamping force, with a cumulative sensitivity index of 93.75%. The study quantitatively identifies the key factors affecting the static buckling response of spacer grids and provides guidance for structural design, parameter prioritization, and reliability optimization.