A new mitochondria-targeted fluorescent probe HCy-D, constructed by dansyl and hemicyanine fluorophores, for SO2 derivatives (HSO3(-)/SO3(2-)) was presented. This probe was designed based on a new FRET platform. HCy-D showed a ratiometric, sensitive and rapid response to HSO3(-)/SO3(2-). Importantly, HCy-D was successfully used for fluorescence imaging of endogenous bisulfite in HepG2 cells, which may benefit cancer diagnosis by discriminating liver cancer cells from normal liver cells.