The strain in curing process of composite part would be influenced by curing compaction, resin flow, curing action and tool-part interaction, meanwhile these factors would also influence the final cured quality of composite part. In this paper, FBG(fiber Bragg grating) sensors are used to in-situ monitoring the strain of composite parts, which are cured in four different pressure situation by autoclave: 0.0Mpa,0.2Mpa,0.4Mpa,0.6MPa. by analyzing the strain change rule, the part quality is predicted, then the predictive result is compared with some verification method: measurement of part’s boundary dimension, ultrasonic phased array scanning, metallographic analysis. The result shows that, the prediction is consistent with verification, the in-situ monitoring method by using FBG sensor is available for predicting cured quality of composite parts accurately: increase curing pressure is benefit of part compaction, resin flow, and reduce delamination,pores in composite part, finally improving the part quality dramatically.