Peroxiredoxins (Prxs) are believed to play an important role in insects for protection against the toxicity of reactive oxygen species (ROS). A gene encoding a novel 1-Cys Prx was firstly identified and characterized from an expressed sequence tag database (EST) in the lepidopteran insect, Bombyx mori. The 1-Cys Prx of B. mori (BmPrx) cDNA contained an open reading frame of 672 bp encoding a protein of 223 amino acid residues with calculated molecular mass of 25 kDa and included conserved cysteine residues signature motifs (PVCT) in the N-terminus amino acid. Sequence comparison showed that BmPrx shared 53 to 64% identity with other species 1-Cys proteins. RT-PCR revealed that the BmPrx transcripts were present in all tissues and developmental stages. The coding sequence was cloned and expressed as a 30-kDa protein in Escherichia coli. The purified enzyme acted as a catalyst in ferrithiocyanate system and protected supercoiled form of plasmid DNA from damage in metal-catalyzed oxidation (MCO) system in vitro. In addition, real-time PCR analysis indicated that significant rise of the transcripts level of BmPrx was induced by temperature stress including low and high temperature stimuli.