This paper describes the experimental assessment of gas permeability of carbon fiber/toughened epoxy laminates under cyclic loadings as a fundamental research for the development of composite cryogenic propellant tank for reusable space transportation system. A thin-ply technique, which may contribute to the enhancement of damage resistance of CFRP laminates, is introduced herein, and the damage accumulation behaviors and gas permeability are compared between thin-ply laminates and standard laminates subjected to cyclic tension and impact.