A Schiff base functionalized α-cyanostilbene derivative (TS) has been synthesized via a simple and straightforward method and characterized by FT-IR, ¹H NMR, ¹³C NMR and mass spectra. TS possessed excellent AIEE properties and exhibited “turn-on” fluorescent responses to Hg²⁺. The results of UV–vis and fluorescence titration experiments revealed that TS was selective and sensitive to Hg²⁺ in pure THF and aqueous environment. The coordination of TS and Hg²⁺ ions generated TS–Hg complex locked the “dancing molecule” because of the flexible chain in the middle of the molecule and the complex was lower soluble induced formation of large aggregates that further limited the non-radiative relaxation channel enhanced emission after adding Hg²⁺ ions in aqueous solution, which had been confirmed by ¹H NMR and dynamic light scattering (DLS).