In this study CAI (Compression After Impact) strength of a carbon/tough-polyimide composite material, MR50K/PETI5, where PETI5 resin was newly developed for the next generation SST at NASA was investigated. First, impact damage was given to CAI specimens at room temperature and the load response was measured during the impact test and the damage of the specimens was observed by an ultra sonic C-scanner and 3-D ultrasonic inspection system. Second, CAI strength and failure strain at room and high temperatures were measured. Third, the damage caused by the CAI test was observed using an optical microscope. Test results are compared with those of T800H/PMR-15 carbon/polyimide composite, where PMR-15 is a typical brittle resin, and the characteristic CAI behavior and strength of a carbon fiber/highly-tough resin composite was clarified.