We aimed to investigate the antiviral activity of Zanthoxylum species against influenza virus A/WS/33, A/PR/8 and B/Lee/40 used by sulforhodamine B (SRB) assay and the action of leaves extracts of Zanthoxylum piperitum on life cycle of influenza virus A/WS/33. Among the twelve extracts, only the leaf extract of Z. piperitum exhibited strong antiviral activity at low concentration of less than 10${mu}g/m{ell}$ with no citotoxicity (50${mu}g/m{ell}$) against all of three viruses. In addition, only oseltamivir showed antiviral activity with $IC_{50}$ of 65.3${mu}g/m{ell}$ against influenza A/WS/33 among the viruses. Furthermore, the leaf extract of Z. piperitum suppressed infection of influenza virus A/WS/33, when added just prior (-1 hr) or after virus inoculation (0 hr). Leaf extract of Z. piperitum directly affect the infectivity of influenza virus A/WS/33 particles. Therefore, Leaf extract of Z. piperitum exhibited higher antiviral activity against three influenza viruses than that of the oseltamivir, which directly interacts with influenza A/WS/33 particles, affecting the initial stages of infection such as receptor binding and virus entry.