Avian influenza is a highly contagious disease of birds caused by A influenza viruses. The circulation in humans by the highly pathogenic H5N1 avian flu in the past few years have caused most pandemics and have heightened fear that the next influenza pandemic is due. Antibodies could be used as an efficient anti-virus agent in clinical therapy. The full-length HA of the A/Jiangsu/1/2007(H5N1) about 1.7 kb was amplified, subcloned to the pFastBac vector and recombinant bacmid DNA was selected. The recombinant HA was expressed and purified HA about 70 ku was used as the antigen to immunize Balb/c mice. The whole H5N1 virus was used to select 5 mono-antibodies (mAbs)，and all of them were tested using microneutralization assays. 8G10D7, one of the antibodies, had broad neutralizing effect against clade 2 and clade 9 H5N1 avian influenza A viruses, and the IC₅₀ was from 1∶256 to 1∶64. When detected with 8G10D7, all 4 viruses showed 70 ku and 43 ku protein band, which confirms that the binding site of the scFv antibodies were located at the HA1 domain. The nucleuses of MDCK cells infected by 4 viruses were colored purple, and red around the nucleus. 8G10D7 showed HI activity to the 4 viruses, the HI has a positive correlation with neutralization concentration IC₅₀, which also further confirms that the binding site of the scFv antibodies were located at the HA1 domain. When the mAb 8G10D7 was used for the study of prophylaxis and therapeutic effect on influenza A viruses infection in an embryonated chicken eggs model. It had a complete 100% protection effect on the H5N1 viruses in avian host in the prophylactic and therapeutic groups. The 100% preventive protection effect could be reached when challenged with H5N1 avian influenza A viruse in human host in the prophylactic groups, and there is also a 87.5% protection effect with H5N1 viruses in human host in the therapeutic groups. Thereby, the study suggests that the mAb 8G10D7 could be used in therapies to counter the H5N1 influenza A virus, and the epitope could be the key point for the design and implementation of vaccines.