A new fluorophore pyrido[1,2-a]benzimidazole was synthesized and used as a ratiometric fluorescent probe based on an intramolecular charge transfer (ICT) mechanism for sensing sulfite. The probe showed high selectivity and sensitivity toward SO₃²⁻ with a fast response time (10 s) and a detection limit of 10.6 nM. Furthermore, the probe showed great potential for the detection of SO₃²⁻ in real samples (dry white wine).