Abstract: A new fluorescence probe, rhodamine cinnamide, was synthesized with rhodamine and cinnamic acid; and structure of the probe was characterized by IR, NMR and MS. In a HEPES buffer solution of pH 7.0 containing 30% (φ) ethanol, a complex with molar ratio of 1 to 1 was formed by the reaction of the probe with Hg2+. Linear relationship between values of fluorescence intensity and concentration of Hg2+ was found in the range within 1.0×10-6mol·L-1 measured at the wavelength of 584 nm (λem), with limit of detection of 7.4×10-9mol·L-1. It was found that this fluorescence probe exhibits highly selective toward Hg2+, and the determination of Hg2+ was not interfered by other metal ions.