In this study, probabilistic analysis and experimental tests are conducted to predict the probabilistic deformation and strength of composite pressure vessels subjected to inner pressure loading. For a probabilistic evaluation of deformation and strength, an integrated probabilistic progressive failure analysis code has been developed. The material non-linear laminated shell theory, progressive failure model, Monte-Carlo simulation, and Edgeworth expansion method have been integrated into the probabilistic strength analysis code. Probabilistic progressive failure model is also incorporated with a commercial FEA code (ABAQUS) to predict the reliability of composite pressure vessel including an AFT dome part. The probabilistic analysis code considers the uncertainties in material properties as well as in the composite fabrication process parameter. Three design random variables with uncertainties were selected: (1) composite elastic constants, (2) lamina strength; and (3) the thickness of the helical and hoop layer. In addition, volumetric size effect on the fiber strength is considered in the design random variables. As an analytical method, the Weibull weakest link model and the modified sequential multi-step failure model are considered and mutually compared. The accuracy of probabilistic analysis was verified by comparing the predicted results with the experimental hoop strain or with the burst pressure obtained by a hydro-test with ten composite pressure vessels. The sensitivities of each response to the design random variables were evaluated and conclusions are drawn concerning the relative importance of these variables in the design problem. Improvement of the structural design based on the probabilistic analysis is also discussed.