Abstract: Till now the processing of advanced composite is still empirical due to its complicated physical and chemical change. In order to transform the processing technique from an empirical state to a transparent, scientific and intelligent approach, the idea of monitoring the cure process of the composite products with fiber optic sensing technique is put forth. A fiber optic refractive sensor was developed and a portable instrument for the optic emission, signal receiving and interogation was integrated to meet the requirement of on-site application. With it the cure process of resin and fiber reinforced prepregs can be monitored. Tests of resin cure process monitoring are carried out with both the resin that should be cured under room temperature and the resin that should be cured under high temperature. The results of tests with resin cure under temperature were compared with the results of Michelson interferometer tests under similar circumstances, which are in good consistency. Tests were also carried out in composite manufacture, in which the fiber optic refractive sensors were embedded in the prepreg during the cure process. It is proved that with this method the key information of the cure process can be extracted out during the process and can be used in on-line intelligent control. In conclusion, this technique can be used not only in the establishment of the cure routine but also in the in-situ monitoring and control of the composite manufacture process.