In situ imaging of biological indicators is imperative for pathological research by utilizing an activatable photoacoustic (PA) probe. However, precise imaging in actual applications is hampered by the inevitable poor accumulation and low sensitivity. Herein, an amphiphilic molecular probe (AP) was rationally constructed as proof of concept for in situ imaging of drug-induced liver injury, which consists of a hydrophilic target unit and a superoxide anion radical (O2•-)-sensitive small-molecule PA moiety. The probe AP successfully realizes the selectivity and sensitivity toward O2•- in vitro and in living cells. Notably, the amphiphilic probe AP can be selectively retained in the liver and activated toward endogenous O2•- through receptor-mediated endocytosis inside hepatocytes. By virtue of the highly efficient accumulation at the liver, AP was further applied to assess isoniazid-induced liver injury through desired ratiometric PA signals. In addition, based on the fluctuation of O2•-, the therapeutic efficacy of hepatoprotective medicines for hepatotoxicity was analyzed in vivo. Therefore, the O2•–specific probe could serve as a promising molecular tool for early diagnosis study of other liver diseases and analysis of new potential therapeutic agents.