Abstract: This paper studied the near-infrared reflectance spectroscopy of glass-fiber reinforced phenolic resin prepreg. The mathematical models between near-infrared spectral parameters and resin content, pre-curing degree and volatile content are built up and the effects of the analysis accuracy were investigated using the chemometrics method. It was found that average absolute errors of the three estimate outcomes were under 0.74 %,1.18 % and 0.26 % respectively. The above results show the feasibility of the near-infrared analytic technology for detecting the quality of composite prepregs.