We have identified phenolic compounds (PCs), particularly phenolic aldehydes, as key mediators of cellulase crosslinking, which significantly influences lignocellulosic biosaccharification. Using the β-glucosidase CaBglA as an example, we incubated it with PCs and employed mass spectrometry to qualitatively identify the crosslinked bands, followed by MS-MS analysis to determine the specific crosslinking sites.