The　nanosized　metal-organic　particles　(NMOPs)　recently　have　attracted　tremendous　attentions　in　biomedical　applications.　However,　few　studies　have　developed　metal-organic　nanoparticles　(NMOPs)　as　near-infrared　(NIR)　II　phototherapeutic　agents　and　as　Fenton-like　agents　for　cancer　theranostics.　Herein,　directly　using　organic　dye　and　Cu(II)-ion　complexes　to　construct　NMOPs,　as　dual-mode　therapeutic　agent　for　PA　imaging-guided　photochemotherapy　in　NIR　II　window,　is　reported.　The　NMOPs　are　simply　an　assembly　of　Cu(II)　ion　and　tetrahydroxyanthraquinone　(THQ)　complexes　[Cu(II)-THQ]n　through　the　coordination　effect,　van　der　Waals　force,　and　π-π　interactions.　After　modification　of　polyethylene　glycol　(PEG-(NH2)2),　the　obtained　Cu-THQNPs　endow　excellent　biocompatibility　and　stability　in　physiological　conditions.　Because　of　the　strong　absorption　at　NIR　II　window　and　photoinduced　electrontransfer　(PET)　mechanism,　the　Cu-THQNPs　not　only　acted　as　an　excellent　photothermal　agent　with　extremely　high　light-to-heat　conversion　ability　(51.34%)　at　1064　nm　for　phototherapy　but　also　explored　as　the　PA　contrast　agent　for　precisely　tracking　and　guiding　the　therapy　in　vivo.　Most　strikingly,　our　Cu-THQNPs　can　be　degraded　by　tumor-specific　acidic-cleaving　of　the　coordination　bonds　and　follow　by　the　slow　release　of　Cu(II)　into　tumors,　which　can　act　as　Fenton-like　agents　to　generate　•OH　from　H2O2　for　enhancing　the　antitumor　efficacy　in　vivo.　With　almost　100%　prevention　of　the　tumor　growth　for　ca.　14　days　and　no　obvious　toxicity　based　on　blood　biochemical/histological　analysis,　this　work　highlights　the　Cu-THQNPs　as　an　efficient　NIR　II　therapeutic　agent　for　precise　cancer　theranostics.　©　2018　American　Chemical　Society.