Our country is the HPAI non- epidemic area currently, have never also found H5 or the hennery of the H7 infections before, but several henneries broke out the H5N2 subtype LPAI in January~Febrauary of this year (2004), although the LPAI will not cause the caponizing infect with a great deal of death, find by recent years other HPAI explosion example, the LAPI may chop round into the HPAI. So this project will focous in monitering on native chicken farms, because of their special feeding mode, that causing bird's flu virus not easy been clear. We will collect some strains of the field AIVs and after passaged in lab chicken AIVs to analysing their virulation.