Abstract: To accurately evaluate the stability of offshore compressed air energy storage (CAES) caverns, this study aim to propose a calculation method for the ultimate anti-uplift bearing capacity of offshore CAES caverns considering internal high-pressure gas leakage. Based on the upper bound theorem of limit analysis, assuming the rock mass failure surface is a curved surface, a calculation model for ultimate uplift resistance bearing capacity is established, incorporating high-pressure gas leakage, pore water pressure, and the nonlinear mechanical properties of the rock mass. Fick’s second law is employed to describe the pressure distribution of high-pressure gas leakage, while Hoek-Brown strength criterion is used to quantify the failure characteristics of the rock mass. The Runge-Kutta numerical method combined with an analytical solution is adopted to solve the failure surface morphology and ultimate internal pressure, while the Morris sensitivity analysis is applied to identify key influencing parameters. The results indicate that the calculation of the Norwegian criterion is relatively conservative, whereas the proposed method, which accounts for the nonlinear response of the rock mass and gas leakage effects, yields results more consistent with engineering practice. Gas leakage significantly influences the ultimate bearing capacity of the caverns, and the bearing capacity gradually converges as the leakage degree decreases. Rock stratum burial depth, geological strength index (GSI), and Biot coefficient are the key parameters affecting the ultimate bearing capacity, among which the geological strength index exhibits the most significant nonlinear influence. The calculation model and analysis method proposed in this study can provide theoretical support for the uplift stability design and safety assessment of offshore CAES caverns.