Animal glue,eggs,and milk were often mixed in ancient China as cementitious materials in painted cultural relics. To explore the interaction of mixed binders and the stability under light aging conditions,to understand the deterioration mechanism of polychrome relics,the stability and protein secondary structure of egg-animal glue,milk-animal glue,and milk-egg mixed binders were characterized by Scanning electron microscopy,FTIR and TG analysis. The results showed that after mixing,the above binders thermal stability and light stability were significantly increased. The infrared spectrum results show that spectral peak broadening after aging of the sample,and the amide Ⅰ band of the protein characteristic spectrum with a wavenumber range between 1 600~1 700 cm-1 shifts towards the wavenumber direction. The Gaussian fitting results of the amide Ⅰ band show that with the change of mixing ratio,the content of ordered structure in the mixed binders shows a trend of first increasing and then decreasing. In the samples with the highest ordered structure content,the random curl structure content also reaches a lower level. At the same time,when the mixing ratio of egg and animal glue is between 1∶1 and 1∶2,the content of the ordered structure is higher than any single binders,with a maximum content of 64.87%,indicating its strongest stability. The content of the secondary structure of protein in the aged binders has changed. The α-helix structure shows a downward trend,while the random curl structure shows a significant increase. The α-helix structure in several mixed binders is still higher than that of a single binder material,indicating that the mixed binders have a certain degree of stability. The results of Thermogravimetric analysis also showed that the thermal stability of the mixed binders before and after aging was higher than that of the single binders,presumably because the protein in the mixed system combined with the lipid in eggs and milk and the interaction between protein and lipid further promoted the stretching and rearrangement of protein molecular structure,which improved the stability. From the stability perspective,the reason for the mixed-use of adhesive materials in painted cultural relics was explained,providing a reference for studying ancient adhesive materials aging mechanism and protection methods.