The twist genes are an evolutionarily conserved group of regulatory basic helix-loop-helix (bHLH) transcription factors. In present study, the twist gene was firstly cloned from Bombyx mori and was designated as BmTwist. Sequence analysis showed that BmTwist cDNA contains a 798 bp open reading frame, encoding a peptide of 266 amino acid residues. Sequence alignment showed that BmTwist protein shared extensive homology with other invertebrate Twist proteins in bHLH motif. RT-PCR and western blot analyses revealed that BmTwist expressed in all developmental stages of B. mori larvae various larval tissues. Here the authors also presented the results of prokaryotic expression, purification, and polyclonal antibody production of the BmTwist protein. Immunofluorescence of BmTwist in BmN cells using the antibodies showed that BmTwist protein was located in both the nucleus and cytoplasm. Furthermore, using B. mori nuclear polyhedrosis virus (BmNPV) baculovirus expression system, the authors expressed a recombinant twist protein in BmN cell line. The obtained results, especially the preparation of polyclonal antibodies against BmTwist, will greatly facilitate further studies to explore biological functions of BmTwist protein such as identifying its potential binding partners.