Abstract: The surface morphologies of two T800 carbon fibers produced from polyacrylonitrile by dry-jet wet spinning and wet spinning were compared. The mechanical properties of Naval Ordnance Laboratory (NOL) rings made from their composites with an epoxy resin matrix, and the strain distributions and hydrostatic breaking pressures of filament-wound pressure vessels produced from them were investigated. Results indicated that dry-jet wet spinning resulted in carbon fibers with a smooth surface while wet spinning gave rise to many surface grooves with uneven widths and depths on the fiber surface. Comparing the two fibers in epoxy resin composite NOL ring tests, those with the wet-spun T800 carbon fibers were more brittle, but had a higher interlaminar shear strength. A filament-wound pressure vessel using the wet-spun T800 carbon fibers was easier to burst at a place located between the dome and the cylinder while that using the dry-jet wet-spun carbon fibers was burst without a preferred broken location in a hydrostatic test. For a 150 mm diameter filament-wound pressure vessel made of the T800 wet-spun carbon fibers, the performance factor (PV/W_c, where P is pressure, V is the volume and W_c is the composite weight) is 34.8 km, which is significantly lower than one made using the T800 dry-jet wet-spun carbon fibers (47.2 km), indicating that the dry-jet wet spun carbon fibers are more suitable for preparing a filament-wound pressure vessel.