The rapid and accurate detection of the H1N1 influenza virus is a key link in epidemic prevention and control. This study innovatively constructed a cascade signal amplification biosensor based on DNA polymerase activity regulation, aiming to achieve ultra-sensitive and highly specific detection of viral nucleic acids. This biosensor has the following significant advantages: (i) Molecular lock-key regulation mechanism: A functional DNA inhibitor is designed to form a complex with Taq DNA polymerase, and the target H1N1 RNA is specifically recognized to release enzyme activity inhibition, converting the target presence information into a PER reaction initiation signal. (ii) Cascade signal amplification system: The single-stranded DNA generated by PER activates Cas12a trans-cleavage activity, achieving a three-level signal amplification of enzyme activity activation → nucleic acid synthesis → CRISPR cleavage. The biosensor exhibits a linear detection range between 1 pM and 1?μM, with a detection limit of 25 fM. Moreover, the platform showed high versatility and could be readily adapted for the detection of other pathogens such as SARS-CoV-2 by simply modifying the nucleic acid sequences of the inhibitor and activator. This study not only provides a new tool for the screening of H1N1 influenza virus, but also offers a novel strategy for the development of next-generation molecular detection technologies suitable for point-of-care diagnostics, indicating considerable application potential.