Photodynamic therapy (PDT) has become an attractive tumor treatment modality because of its noninvasive feature and low side e®ects. However, extreme hypoxia inside solid tumors severely impedes PDT therapeutic outcome. To overcome this obstacle, various strategies have been developed recently. Among them, in situ oxygen generation, which relies on the decomposition of tumor endogenous H2O2, and oxygen delivery tactic using high oxygen loading capacity of hemoglobin or per°uorocarbons, have been widely studied. The in situ oxygen generation strategy has high speci¯city to tumors, but its oxygen-generating e±ciency is limited by the intrinsically low tumor H2O2 level. In contrast, the oxygen delivery approach holds advantage of high oxygen loading e±ciency, nevertheless lacks tumor speci¯city. In this work, we prepared a nanoemulsion system containing H2O2-responsive catalase, highly e±cient oxygen carrier per°uoropolyether (PFPE), and a near-infrared (NIR) light activatable photosensitizer IR780, to combine the high tumor speci¯city of the in situ oxygen generation strategy and the high e±ciency of the oxygen delivery strategy.