Flour paste is the most widely used adhesive in the mounting and restoration of painting and calligraphy relics. In this study, ultraviolet absorption spectrometry, infrared spectrometry, and scanning electron microscopy were used to analyze the effect of flour paste on mounted painting and calligraphy works, with the aim of clarifying the relationship between the paste properties and the deterioration of mounted painting and calligraphy works. The results show that:1) hydrogen bonds formed between the hydroxyl groups of starch and the fibers of Xuan paper, giving the paste both bonding and strengthening properties; 2) during deterioration, the aggregation state of starch molecules changed, the degree of internal crystalline structure ordering decreased, and the mass ratio of amylose to amylopectin first decreased and then increased; and 3) the color difference and elastic modulus of the mounted painting and calligraphy works increased, making them more prone to physical deterioration such as discoloration, creasing and fractures during long-term preservation. This study provides theoretical guidance for the scientific application and performance improvement of paste in traditional craftsmanship.