The development of biodegradable nanomaterials for near-infrared photothermal antibacterial is of great significance to improve the biosafety of nano-antibacterial strategies in clinical application. In this study, a new nano-antibacterial strategy was developed, in which a biodegradable charge-transfer nanocomplex acted as a high-efficiency near-infrared light-activatable photothermal nanoconvertor. The charge-transfer nanocomplex was synthesized through oxidation-induced self-assembly of 3,3',5,5'-tetramethylbenzidine molecules. This nanocomplex can efficiently convert light energy around 900 nm into heat energy, with a photothermal conversion efficiency of up to 30%. More importantly, the nanocomplex can spontaneously degrade under physiological conditions within 12 hours. Utilizing the photothermal effect of this nanocomplex, both Gram-positive bacteria and Gram-negative bacteria can be inactivated within 2 minutes. In addition, the inactivation mechanism was systematically discussed and the results indicated that the photothermal effect induced bacterial cell membrane damage was probably responsible for the antibacterial effect.