Abstract: A fluorescent probe (F1) based on rhodamine derivative was synthesized for recognition of Hg²⁺. When equivalent Hg²⁺ (10 μmol·L^-1) was added in the medium of acetonitrile (1+1) solution, the probe F1 showed obvious absorption peak at 561 nm. The fluorescence intensity (λ_ex=550 nm, λ_em=580 nm) increased 7.5 times, and the solution changed from colorlessness to pink, because chelation of Hg²⁺ with rhodamine spherolases initiated ring opening. Other common metal ions did not interfere recognizing Hg²⁺ with probe F1. Within a wide range of acidity, linear relationship was found between the fluorescence intensity with Hg²⁺ concentration in the range of 0.2-8 μmol·L^-1. The detection limit (3σ/s) was 0.15 μmol·L^-1.