This paper presents the preparation of a pyrazoline compound and the properties of its UV-Vis absorption and fluorescence emission. Moreover, this compound can be used to determine Hg(2+) ion with selectivity and sensitivity in the EtOH:H2O =9:1 (v/v) solution. This sensor forms a 1:1 complex with Hg(2+) and shows a fluorescent enhancement with good tolerance of other metal ions. This sensor is very sensitive with fluorometric detection limit of 3.85 × 10(-10) M. In addition, the fluorescent probe has practical application in cells imaging.