The present invention relates to an avian influenza virus miRNA and the identification, detection and application thereof. In particular, a kind of specific microRNA, miR-HA-3p, is screened for the first time through detecting the microRNA expression levels in samples of animals with avian influenza. The experiments prove that the miR-HA-3p, as a microRNA marker, can be very effective in detecting avian influenza virus and avian influenza. Furthermore, inhibiting the function of miR-HA-3p can be very effective in relieving symptoms of avian influenza and treating avian influenza. The microRNA revealed in the present invention for the first time can be developed into a detection agent and a therapeutic agent as well as the corresponding kits for the detection and treatment of avian influenza (e.g., H5N1).