The core effector protein, Cas9 of the CRISPR/Cas9 system is capable of recognizing and cleaving target DNA sequences under the guidance of guide RNA (gRNA). This study developed a novel platform for detecting influenza A virus (H1N1) based on CRISPR/Cas9 trans-cleavage activity and nuclease-mediated strand displacement amplification. The designed DNA hairpin (HP) structure triggers the rearrangement of the target fragment acid conformation, enabling cyclic amplification of the target fragment under the action of Klenow polymerase. The Nt.BbvCI recognition site was introduced into the stem of the HP structure, enabling exponential amplification of nucleic acid signals through a “nicking-extension-replacement” cycle. The amplified products activate the Cas9/sgRNA complex, which subsequently cleaves fluorescent reporter probes, generating signals. Sensitivity testing demonstrated that the platform detection limit was as low as 23 copies/μL, allowing it to specifically distinguish H1N1 from other influenza subtypes. This platform is the first to integrate CRISPR/Cas9 trans-cleavage with strand displacement amplification (SDA) for practical application, making considerable progress and providing a highly sensitive and specific detection method for the early diagnosis of influenza.