The development of imageable photothermal theranostics has attracted considerable attention for imaging guided photothermal therapy(PTT)with high tumor ablation accuracy.In this study,we strategically constructed a near-infrared(NIR)cyanine dye by introducing a rigid cyclohexenyl ring to the heptamethine chain to obtain a heptamethine dye CySCOOH with high fluorescence intensity and good stability.By covalent conjugation of CySCOOH onto human serum albumin(HSA),the as-prepared HSA@CySCOOH nanoplatform is highly efficient for NIR fluorescence/photoacoustic/thermal multimodality imaging and photothermal tumor ablation.The theranostic capability of HSA@CySCOOH was systematically evaluated both in vitro and in vivo.Most intriguingly,complete tumor elimination was achieved by intravenous injection of HSA@CySCOOH(CySCOOH,1 mg kg(-1); 808 nm,1.0 W cm(-2)for 5 min)into 4T1 tumor-bearing mice,with no weight loss,noticeable toxicity,or tumor recurrence being observed.This as-prepared protein-based nanotheranostics exhibits high water dispersibility,no off target cytotoxicity,and good biodegradability and biocompatibility,thus facilitating its clinical translation to cancer photothermal theranostics.