Abstract: A fluorescent reagent of furfural p-nitroaniline (FFNA) was synthesized. In a Na₂B₄O₇ buffer solution of pH 9.06, FFNA reacted with Hg²⁺ to form a complex with the amount-of-substance ratio of 1:1, resulting in fluorescence quenching of FFNA. Based on this fact, a mehtod of fluorescence spectroscopy was developed for determination of Hg²⁺. At the excitation wavelength of 235 nm and emission wavelength of 330 nm, linear relationship was found between the change of the fluorescence intensity with the concentration of Hg²⁺ in the range of 4.0×10^-8-1.1×10^-7mol·L^-1, with detection limit (3s/k) of 2.24×10^-8mol·L^-1. The proposed method was used for the determination of trace mercury in cosmetics samples, giving results in agreement with those obtained by atomic absorption spectrophotometry. Recovery rates obtained by standard addition method were in the range of 99.0%-99.5%, and RSDs (n=6) were in the range of 3.1%-3.5%.