The invention discloses a single-chain antibody ScFv for resisting influenza viruses, a preparation method for the single-chain antibody ScFv, application of the single-chain antibody ScFv, a gene for encoding the single-chain antibody ScFv, a carrier containing the gene, a host cell and the like. The single-chain antibody ScFv for resisting the influenza viruses is one of the following proteins: 1) a single-chain antibody formed by connecting a heavy chain variable region and a light chain variable region of the antibody through a linker peptide, wherein an amino acid sequence of the light chain variable region and an amino acid sequence of the heavy chain variable region are shown as SEQ ID NO.1 and SEQ ID NO.2 in a sequence table respectively; and 2) a derived antibody obtained by improving the single-chain antibody in step 1), wherein the improvement comprises the deletion, substitution or insertion of amino acid, and the derived antibody has the antibody activity of resisting H1N1 influenza viruses. The molecular weight of the single-chain antibody is about 27kD; and the single-chain antibody can specifically identify the H1N1 influenza viruses and block the combination of the viruses and natural serum. The single-chain antibody can be used for diagnosing, preventing, controlling and treating the infection of the H1N1 influenza viruses, or is used for antiviral breeding of transgenic animals.