Background: Dental caries is the most prevalent bacterial biofilm-induced disease. Current clinical prevention and treatment agents often suffer from adverse effects on oral microbiota diversity and normal tissues, predominately arising from the poor biofilm-targeting property of the agents. Methods: To address this concern, we herein report dual-sensitive antibacterial peptide nanoparticles pHly-1 NPs upon acid and lipid-binding for treatment of dental caries. Amino acid substitutions were performed to design the peptide pHly-1. The potential, morphology and secondary structure of pHly-1 were characterized to elucidate the mechanisms of its pH and lipid sensitivity. Bacterial membrane integrity assay and RNA-seq were applied to uncover the antimicrobial mechanism of peptides under acidic condition. The in vitro and ex vivo antibiofilm assays were used to determine the antibiofilm performance of pHly-1 NPs. We also carried out the in vivo anti-caries treatment by pHly-1 NPs on dental caries animal model. Oral microbiome and histopathological analyses were performed to assess the in vivo safety of pHly-1 NPs. Results: The pHly-1 peptide underwent the coil-helix conformational transition upon binding to bacterial membranes in the acidic cariogenic biofilm microenvironment, thereby killing cariogenic bacteria. Under normal physiological conditions, pHly-1 adopted a ??-sheet conformation and formed nanofibers, resulting in negligible cytotoxicity towards oral microbes. However, in acidic solution, pHly-1 NPs displayed reliable antibacterial activity against Streptococcus mutans, including standard and clinically isolated strains, mainly via cell membrane disruption, and also suppressed in vitro and human-derived ex vivo biofilm development. Compared to the clinical agent chlorhexidine, in vivo topical treatment with pHly-1 NPs showed an advanced effect on inhibiting rat dental caries development without adverse effects on oral microbiota diversity and normal oral or gastric tissues. Conclusion: Our results demonstrated the high efficacy of dual-sensitive antimicrobial peptides for the selective damage of bacterial biofilms, providing an efficient strategy for preventing and treating dental caries.