Group of influenza A virus attenuated strains based on synonymous mutation and/or deletion mutation as well as preparation method and application of influenza A virus attenuated strains

The invention relates to a group of influenza A virus attenuated strains based on synonymous mutation and/or deletion mutation as well as a preparation method and application of the influenza A virus attenuated strains. The attenuated strain disclosed by the invention is obtained by modifying an M2 gene; the modification comprises the step of performing synonymous mutation on the overlapped part of the M2 gene and the M1 gene in the M gene of the influenza A virus to ensure that the M1 amino acid sequence is complete and unchanged; or the modification comprises the step of performing synonymous mutation on the overlapped part of the M2 gene and the M1 gene in the M gene of the influenza A virus to ensure that the M1 amino acid sequence is complete and unchanged, and deleting a part of the nucleotide sequence from the M2 gene. The attenuated strain disclosed by the invention is high in stability, free from reverse mutation after multiple passages, high in safety and low in dependence on a cell line, and has re