To identify the types of binder used in the theater color painting of Jiayuguan pass, the Fourier infrared spectra were collected, which of the reference samples consist of leather glue, fish glue, egg white, egg yolk, and casein prepared by traditional technology and three cultural relics samples. The factor analysis combined with the linear discriminant analysis (PCA-LDA) was used to construct the mathematics model and determine the kind of the binder of relics samples. It was found that there was abundant information about the molecular structure in the range of 1 800~1 000 cm-1 of the reference samples infrared spectra. The common infrared spectrum characteristics of protein compounds in this range are the peak of CO bond stretching vibration around 1 650 cm-1, the peak of C—N bond stretching vibration and N—H bond bending vibration around 1 542 cm-1, and the peak of C—N bond stretching vibration around 1 240 cm-1. Besides, due to the fatty substances contained in yolk, skin glue and milk reference samples, there is also a stretching vibration peak of saturated fatty acid ester carbonyl CO bond near 1 745 cm-1. Through the analysis of factor score scatter diagram, it could be seen that there are differences among different reference samples. According to this, factor scores of the reference sample infrared spectrum were used as the training database to calculate the discriminant function by LDA. The group center figures, and cross-validation of the functions were performed and the accuracy of the discriminant equation is 93.3%. Base on the spectrum of three relics samples, which still have the characteristics of protein binder, the spectrum difference between them and reference can be seen due to degradation. PCA-LDA analysis model was used to identify the kinds of the binder for cultural relics, and the results were all leather glue. According to the analysis above, it could be concluded: A stable and effective infrared spectrum discrimination PCA-LDA model can be established for the discrimination of binder. The theater color painting binder used in the Jiayuguan pass was identified as leather glue by this model.