Carbon fiber-reinforced plastics (CFRPs) are used in the aerospace industry as a lightweight substitute for metal materials with high mechanical performance. However, their applicability under extreme-temperature conditions remains constrained by the insufficient thermal resistance of commonly used polymer matrices. This study fabricates CFRP with enhanced thermal stability by introducing a polyimide (PI) matrix with excellent heat resistance and the carbon nanotube (CNT) network through a one-step process. The CNT network restricts segmental motion of polymer chains at the nanoscale, leading to a nanoconfinement effect that enhances the glass transition temperature (Tg). To achieve effective nanoconfinement effect, the CNT content was optimized and resulted in improved thermal stability was confirmed. Furthermore, the effects of the uniformly distributed CNT network on the performance of the CFRPs were investigated by analyzing the mechanical and tribological properties.