NS1 gene was amplified from an H5N1 influenza virus, A/Anhui/01/2005 for cloning, sequence analysis and later expression in Escherichia coli. The result showed that NS1 of A/Anhui/01/2005 strain had the close phylogenetic relationship with that of H5N1 avian influenza strains recently isolated in Fujian and Hunan. Correspondingly, its amino acid sequence showed the highest homology with that of Fujian and Hunan strains. The amino acid position of 92 involved in virus virulence was Asp, contrast to Glu in A/HK/156/97. Five amino acid deletion from 80 to 84 was also found in A/Anhui/01/2005, which was considered as a contributor to virus resistance against cytokine,such as IFN,TNF,etc. A motif binding to CBSF，conveted to GFWEN, which was different from previous GLEWN found in other 19 strains. Besides, the PL motif of ESEV, binding to PDZ domain,is the same as previous high-mortality H5N1 isolates. Furthermore, this NS1 was efficiently expressed in Escherichia coli and the highly purified product demonstrated wonderful activity as confirmed by Western blot. As a result，the work pays the way for further understanding the role of NS1 in human H5N1 infection and development of new antiviral drugs against influenza virus.