Abstract: Synthesis of the fluorescence reagent,N-9-acridinyl-α-aminoacetic acid,was improved,resulting a decrease of time for diazotization from 7 h to 3 h,and an increase of yield from 78.9% to 85.2%.Fluorescence quenching effect was observed when the new reagent was reacted with Cu(Ⅱ).The use of the reagent as a fluorescence probe in the determination of trace amounts of copper was proposed.In a buffer solution of pH 7.0,Cu(Ⅱ) was reacted with the fluorescence reagent in the presence of ethanol,the magnitude of derease in fluorescence intensity (ΔF) of the reaction solution was measured at the wavelengths of (λex) 262.0 nm and (λem) 456.0 nm by taking the difference between emission fluorescence intensity of the blank solution FB and the sample solution FA.Linear relationship between values of ΔF and concentration of Cu(Ⅱ) was found in the range of 0.20-600.0 μg·L-1,with its detection limit (3σ/b) of 0.04 μg·L-1.Values of RSD′s (n=6) and recovery found in the analysis of 3 samples of environmental water,were less than 2.5% and in the range of 96.0%-102.0%.