The development of effective method for monitoring of endogenous hypochlorous acid (HClO) in vivo is of great significance for early diagnosis of lipopolysaccharide (LPS) induced acute liver injury. Herein, we report a polymer micelles-based ratiometric fluorescent probe (PM) based on the combination of intramolecular charge transfer (ICT) mechanism and fluorescence resonance energy transfer (FRET) principle for selective visualization of endogenous HClO in vivo. Upon the reaction of PM with HClO, the electron-donating thiourea moiety is oxidized and transformed into imidazoline moiety (electron-withdrawing group), resulting in a dramatic blue shift (?100 nm) in the fluorescence emission. The as-prepared PM shows good water dispersibility (100% aqueous media), fast response (< 40 s), high sensitivity (a detection limit of 1.75 nM), and outstanding selectivity toward HClO over other ROS/RNS (50 equiv.). In addition, the vivo imaging experiments demonstrate that PM facilitates the visualization of endogenous HClO generation with LPS induced acute liver injury in zebrafish model.