Abstract: An optical fiber sensor system , established by our laboratory , was used to measure the pressure changein the normal direction of prepreg layers to monitor the cure process. The optical fiber sensor is embedded in theprepreg and the change of output voltage can reflect the change of compacting pressure between fibers and the compacting degree of composite laminates. The experimental result s show that the system can not only reflect the pressure change in the normal direction of prepreg layers during cure molding process , but also provide some useful datafor layer consolidation and resin flowing. The data are very important to determine the pressurized point and optimize cure processing and cont rol the performances of composite parts.