Method for attenuating influenza virus by combining synonymous mutation with deletion mutation, attenuated influenza virus strain and application

The invention relates to an influenza virus attenuating method combining synonymous mutation with deletion mutation, an attenuated influenza virus strain and application, and belongs to the technical field of attenuated virus vaccines. The weakening method comprises the following steps: 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, performing termination codon mutation and deleting part of nucleotide sequence in the transmembrane region of the M2 gene, and performing mutation on the M2 gene by using a reverse genetic manipulation system to obtain the influenza A virus. And the attenuated influenza virus strain is rescued. The virus obtained by the attenuating method disclosed by the invention is stable in proliferation process and has no possibility of returning to a wild type; during high-dose virus inoculation, the strain can grow and propagate in MDCK cells, and