Abstract: A fluorescent probe (HBN) capable of recognizing Hg2+ was designed and synthesized using naphthalene isothiocyanate as a recognition and fluorescent group. The structure was characterized by Mass Spectrometry and Nuclear Magnetic Resonance, and Ultraviolet-Visible Absorption Spectrum and fluorescence emission were used, which show various properties of HBN to identify Hg2+. The results reveal that HBN exhibits higher selectivity and fluorescence response to Hg2+ in 50% acetonitrile aqueous solution, and its fluorescence intensity increases with the increase of Hg2+ concentration, which stops when the concentration of Hg2+ is two times the concentration of the probe. In the same time, the new compound was detected by mass spectrometry, indicating that HBN belonged to reactive fluorescent probe of Hg2+.