Triple-A polyimide (TriA-PI) concept, “amorphous, asymmetric, and addition type”, was originally proposed by Yokota in 1999 for high temperature polymer matrix composites. The first version polyimide “TriA-PI-1” was developed from a-BPDA (2,3,3′,4′-biphenyltetracarboxylic dianhydride), 4,4′-oxydianiline (4,4′-ODA), and phenylethynyl phthalic anhydride (PEPA). The cured polyimide exhibits excellent mechanical properties with high glass transition temperature. In this study, a new prepreg system, namely imide-oligomer dry prepreg was developed by impregnating imide-oligomer into unidirectional carbon fiber bundles directly. Carbon fiber/TriA-PI-1 composites were fabricated from the imide-oligomer dry prepreg, and mechanical properties were evaluated. It was demonstrated that the TriA-PI-1 composite exhibits excellent compressive and tensile strengths at 300 °C as well as room temperature. It was easy to make a high quality composite laminate without complicated process using imide-oligomer dry prepreg.