New novel fire-resistant and heat-resistant cyclotriphosphazene-containing polyimide resins were prepared in situ by the polymerization of (p-aminophenoxy)(phenoxy)cyclotriphosphazenes with 3,3',4,4'-benzophenonetetracarboxylic acid or 3,3',4,4'-diphenylsulfonetetracarboxylic acid and a crosslink agent, 5-norbornene-2,3-dicarboxylic acid and were used as polymer matrix compositing with a woven carbon fiber to prepare nadic-end-capped cyclotriphosphazene-containing polyimide/carbon fiber composites. The thermal stability, flame retardance, morphology of the surface fracture, and some physical properties of the composites were investigated by thermogravimetric analysis, scanning electron microscopy, and a material testing system, respectively. The composites had good thermal stability, flame retardance, and mechanical properties. (C) 2003 Wiley Periodicals, Inc.