Abstract: When supercavitating vehicles cruise deeply under water with high speed, they will undergo high longitudinal force and circumferential pressure caused by ventilated cavity, which may result in structural buckling. The uncertainty of structural parameters and the ventilated cavitation number should be considered by performing structural buckling reliability analysis of vehicle compartments. The vehicle compartment with stiffening rings is simplified as thin cylindrical shell with variable thickness, and then the critical buckling load coefficient is obtained by semi-analytical finite element method. Buckling reliability index is obtained by hybrid method of stochastic finite element and limit step length iteration method. Numerical results show (1) buckling reliability index increases greatly with the increase of the ring number and it is mainly affected by the axial constraint if both ends of the compartment are simply supported, (2) buckling reliability index declines with the increase of operation depth and can be enhanced by controlling the uncertainty of thin shell thickness, elastic modulus and stiffening rings thickness, and (3) it is complex how buckling reliability index is affected by the uncertainty of the ventilated cavitation number.