To investigate the bearing behavior of grouted connections in jacket foundations, a prototype test was conducted based on an actual offshore wind power project, explicitly accounting for the influence of installation eccentricity commonly encountered in engineering practice. Furthermore, finite element analysis (FEA) was performed to investigate the effects of parameters such as installation error, grouting material strength, steel strength, and jacket leg wall thickness on the axial mechanical performance of the grouted connection. The applicability of current code formulas was also compared and evaluated. The experimental results indicate that although the additional bending moment caused by installation eccentricity leads to local micro-compressive strain, it does not weaken the macroscopic mechanical performance of the structure. Parametric analysis reveals that the grouted connection exhibits strong robustness against construction installation errors. Increasing the yield strength of the steel can significantly improve the ultimate bearing capacity of the structure, whereas simply increasing the strength of the grouting material yields limited gains. Additionally, while increasing the wall thickness of the jacket leg can enhance bearing capacity, there is a clear law of diminishing marginal returns. The API and HSE code formulas risk overestimating the bearing capacity of grouted connection sections using high-strength grouting materials. While the DNV code is conservative, it effectively covers the size effect of large-diameter structures and is more suitable as a safety baseline for engineering design.