Nanozymes are effective novel antibacterial agents. However, they still have some shortcomings such as low catalytic efficiency, poor specificity, and non-negligible toxic side effects. Here, we synthesized iridium oxide nanozymes (IrO_x NPs) by a one-pot hydrothermal method and used guanidinium peptide-betaine (SNLP/BS-12) to modify the surface of IrO_x NPs (SBI NPs) to obtain a high-efficiency and low-toxicity antibacterial agent. In vitro experiments showed that SBI NPs with SNLP/BS12 could enhance IrO_x NPs to target bacteria, mediate bacterial surface catalysis and reduce the cytotoxicity of IrO_x NPs to mammalian cells. Importantly, SBI NPs were able to effectively alleviate MRSA acute lung infection and effectively promote diabetic wound healing. Accordingly, iridium oxide nanozymes functionalized with guanidinium peptides are expected to be an effective antibiotic candidate in the postantibiotic era.