Protein misfolding and abnormal self-assembly lead to the aggregates of oligomers, fibrils, or senior amyloid β (Aβ) plaques, which are associated with the pathogenesis of many neurodegenerative diseases. Progressive cerebral accumulation of Aβ protein was widely proposed to explain the cause of Alzheimer's disease, for which one promising direction of the preclinical study is to convert the preformed β-sheet structure of Aβ aggregates into innocent structures. However, the conversion is even harder than the modulation of the amyloidosis process. Herein, a graphene oxide/carbon nitride composite was developed as a good photocatalyst for irreversibly disassembling the Aβ aggregates of Aβ(33-42) under UV. Quartz crystal microbalance, circular dichroism spectrum, atomic force microscopy, fluorescent spectra, and mechanical property analysis were performed to analyze this photodegradation process from different aspects for fully understanding the mechanism, which may provide an important enlightenment for the relevant research in this field and neurodegenerative disease study.