A multifunctional reactive fluorescent probe DTB was constructed for biosensing, aggregation inhibition, and toxicity alleviation of β-amyloid. The synergistic effect of hydrophobic interaction and covalent interaction makes DTB have more stable binding and better selectivity to Aβ. The detoxification effect of DTB on Aβ aggregates was also verified in live nerve cells and microglia cells. Furthermore, DTB exhibits an excellent staining of Aβ plaques.