Objective To evaluate the pathogenicity, transmission ability, and phylogenesis of the dead black headed gull isolated new emerging infectious H5N1 virus which was existed in the end of 2011.Methods To verify whether the dead black headed gull isolated H5N1 could infect human source cells, and investigate the replication ability, virulence and pathogenicity in MDCK cells and BALB/c mouse model. Meanwhile, the transmission ability of the new emerging infectious H5N1 will be tested using mouse model. Meanwhile, phylogenetic analysis was done based on HA protein sequence. Results The new emerging H5N1 virus could replicate in some human lung cell lines, and the pathogenicity to BALB/c mice is weaker than the most virulent H5N1 strain and the vaccine preparation strain. However, the new virus could be efficiently transmitted among mice, but the protective antibody could not be detected in mice.Conclusion Phylogenetic analysis based on HA amino acid sequences showed it belong to clade 2.3.2.1, which is the main epidemic group in recent years.