Serpins from pathogens have been implicated in evasion of the host immune system. We identified a new serpin protein (NbSPN106), analyzed its sequences, and detected using Western blotting.Nosema bombycis proteins with an expect score less than 1 x 10(-5) were checked against MEROPS database (http://merops.sanger.ac.uk) by Local Alignment Search Tool search and confirmed with Database of Protein Families and HMMS. Multiple sequence alignments were performed using the ClustalX. The sequence encoding the mature protein was amplified by PCR, cloned into the pGEX4T-1 vector and expressed in Escherichia coli. Specific antiserum generated against the recombinant protein was used in immunoblot assay.A new serpin gene, named NbSPN106, was identified form Nosema Bombycis genome. The coding sequence of this gene is 1155 bp length with a putative signal peptide and contains the conserved serpin sequences. A specific band of approximately 45 kDa was recognized by the anti-NbSPN106 serum.The finding of serpins in Nosema bombycis raises new questions about their possible role in pathogenicity, which deserves further studies.