Influenza virus poses a potential risk of triggering the next global pandemic. In-depth investigation into the mechanisms underlying influenza virus replication and pathogenicity will provide robust support for controlling influenza virus infection. Although post-translational modifications are known to regulate viral infection, the role of lactylation in influenza virus replication remains elusive. In this study, influenza virus ribonucleoprotein complex subunits are found to be lactylated. Specifically, ATAT1 promotes viral polymerase acidic protein (PA) lactylation and enhances viral replication. In contrast, SIRT1 mediates de-lactylation of PA and exerts an inhibitory effect on viral replication. Further investigations reveal lactylation of PA at residues K605 and K609 is essential for viral replication and pathogenicity. Mechanistically, PA K605/609 residues are localized at the interaction interface of the ANP32-mediated polymerase asymmetric dimer; mutation at these residues inhibits polymerase asymmetric dimerization, thereby impairing RNA production during viral genome replication. Collectively, this study uncovers a novel mechanism by which influenza virus hijacks host enzymes to mediate PA lactylation, and expands the molecular regulatory network of influenza virus infection.