In this work, we report a fluorescent probe (TPEQN-P) for detecting alkaline phosphatase (ALP) with high sensitivity and monitoring its activity based on the specific aggregation-induced emission (AIE) effect. TPEQN-P can be constructed by conjugating the phosphate moiety into an AIE molecule (TPE-QI) through a reactive p -hydroxybenzyl group, which exhibits very weak emission in aqueous media due to its good water solubility. In the presence of ALP, TPEQN-P undergoes dephosphorylation and releases the hydrolysis product TPE-QI, which is intensely fluorescent because of its poor water solubility. The detection limit for ALP using TPEQN-P can be as low as 0.0077 U L -1 with a linear range of 0-30 mU mL -1 in solution. TPEQN-P also shows excellent applicability in serum samples, demonstrating potential applications in clinical diagnosis and biomedical research. TPEQN-P also can be applied for the determination of ALP activity and in ALP inhibitor screening.