Influenza A virus is one of the major pathogens that pose a large threat to human health worldwide and has caused pandemics.Influenza A virus is the Orthomyxoviridae prototype,and has 8 segmented negative-sense singlestranded RNA (vRNA) as its genome.Influenza virus RNA polymerase (RdRp) consists of three subunits PB2,PB1 and PA,and catalyzes both transcription and replication.Recently,intensive biochemical and structural analysis of its RdRp has been performed.In this paper,we review the details from the biochemical analysis of the purified influenza virus RdRp and the classical ribonucleoprotein complex,as well as piece together their structures to form an overall picture.