Polydopamine fluorescent nanoparticles(F-PDA) were prepared with dopamine hydrochloride by oxidation under alkaline conditions.The F-PDA@MnO2 complex was prepared by combining F-PDA with manganese dioxide(MnO2) nanosheets.Based on this,a fluorescent probe based on F-PDA@MnO2 complex was constructed for the detection of acetylcholinesterase(AChE) as the fluorescence of F-PDA could be quenched by adding MnO2 nanosheets.In the presence of acetylthiocholine iodide(ATCh),the fluorescence of F-PDA was restored after adding AChE.Results showed that there was a good linear relationship for fluorescence recovery of the probe with AChE in the concentration range of 5-100 mU/mL,and the detection limit(S/N=3) was 014 mU/mL.The probe was applied in the detection of AChE in buffer solution with high selectivity.The recoveries were in the range of 89.5%-120%with the relative standard deviations(RSD) of 1.6%-2.5%.The research results provide a new methodological model for the construction of sensing system based on F-PDA.