<p>Wheat starch-based paste is a traditional adhesive used in paper relic conservation. This study systematically investigates the effects of three key parameters (mass fraction, protein content, and gelatinization temperature) in wheat starch-based paste on the degradation behavior of Xuan paper. ATR-FTIR characterized the molecular structure of Xuan paper after separate starch and flour treatment. Through a 2³ factorial experimental design, we demonstrate that mass fraction serves as the primary factor controlling paper lightness loss, yellowing, color change increase, and acidification, while protein content predominantly governs the reduction in 400 nm reflectance. Protein conformational changes indicated by fluorescence red shifts and a shift from α-helix to random coil structures were key factors in loss of film flexibility. After 17-day degradation, paste-treated paper showed more severe degradation in optical properties and developed microcracks, contrasting with untreated paper in wettability and crystallinity. The work provides a framework for understanding wheat paste-induced paper degradation.</p>