BODIPY and coumarin were assembled into a single scaffold that was cleaved upon oxidation by ClO-, thereby enabling ratiometric fluorescent detection ClO−. The ratiometric fluorescence response was distinctive (|510/|660=18.3) in the presence of ClO-. It was accompanied by an obvious solution color change from dark-blue to colorless. The probe is highly selective and sensitive towards ClO-, with a rapidly response time. Moreover, imaging experiments in live HeLa cells showed that the probe could readily penetrate the cell membrane and was amenable to real-time imaging of ex/endogenous ClO-. Importanty, the probe was successfully used to detect ClO- in vivo via imaging an arthritis nude mouse model.