Aluminum ion complexed 5,8-di-Br-hypocrellin B is a new water-soluble perylenequinonoid derivative with enhanced absorption over hypocrellin B (HB) in the phototherapeutic window (600–900 nm). Electron paramagnetic resonance and 9,10-diphenyl-anthracene bleaching methods were used to investigate the photosensitizing activity of [Al₂(5,8-di-Br-HB)Cl₄]_n in the presence of oxygen. Singlet oxygen, superoxide anion radical and hydroxyl radical can be generated by [Al₂(5,8-di-Br-HB)Cl₄]_n photosensitization. Singlet oxygen (¹O₂) is formed via energy transfer from triplet-state [Al₂(5,8-di-Br-HB)Cl₄]_n to ground-state molecular oxygen. ¹O₂ participates in the generation of a portion of superoxide anion radical (O₂^·−). Besides superoxide anion radical (O₂^·−) may originate from the electron transfer between the triplet-state [Al₂(5,8-di-Br-HB)Cl₄]_n and the ground-state molecular oxygen. ^·OH is formed through the Fenton–Haber–Weiss reaction and the decomposition of DMPO–¹O₂ adduct. Compared with HB [Al₂(5,8-di-Br-HB)Cl₄]_n primarily remains and enhances the generation efficiency of superoxide anion radical and hydroxyl radical but that of singlet oxygen decreases.