Abstract: Avian influenza A virus（AIV） is species-specific and usually only infects poultry. However, with the adaptive evolution of AIV,several pandemics of AIV between poultry and humans have been reported in the 20 th century, posing a huge threat to human health. The adaptive evolution of AIV is regulated by many factors, including some host factors and some proteins of the virus itself. The adaptive evolution of AIV has many impacts on the receptor binding characteristics, pathogenicity, and transmission ability of the virus etc.,which causes the host-specific change of the virus, and then cross-species transmission. This article reviewed the adaptive evolution, cross-species transmission and related determinant factors of AIV,in order to provide theoretical support for AIV outbreak early warning and vaccine development.