Bisulfite (HSO 3 À )i so ne of the main forms of sulfur dioxide in physiological systems. Two2 -(2'-hydroxyphenyl)benzothiazole-derived fluorescentp robes bearinganitroolefin moiety were designed based on the intramolecular charge transfer (ICT) effect and excited-state intramolecular proton transfer (ESIPT) mechanism to afford af luorescent turn-on response specifically in the present of HSO 3 À ions. Owing to the remarkable ICT effect from hydroxy group to the nitro group, the probese xhibit extremelyw eakf luorescence. Upon the conjugate addition reactionw ith HSO 3 À at the nitroolefin moiety of the probes, the ICT characteri s weakened and the absorption spectra of the products are blueshifted. Ap ronounced fluorescence enhancementb ased on ESIPT was also observed. The two probese xhibitedg ood sensitivity,h igh selectivity and an excellent anti-interference properties of their large Stokes shifts,i ndicating that the probesa re highly suitable for biological systems. Furthermore,t hey were successfully applied to the imaging of HSO 3 À in living cells.