Abstract 【Aim】 The Sox family is a group of transcription factors and plays essential roles during the development of multicellular animals. This study aims to clone a Sox family gene from the silkworm, Bombyx mori, and to explore its expression pattern and function in different larval tissues and developmental stages of the silkworm. 【Methods】 A gene of the Sox family was cloned from the silkworm using rapid amplification of cDNA ends (RACE) and its sequence was analyzed with bioinformatics tool. The prokaryotic expression vector was constructed to induce the expression of protein and produce its antibody to test the expression characteristics of the protein during the embryonic development (24, 48, 72, 96, 120, 144, 168, 192 and 216 h after oviposition) and newly hatched larvae of the silkworm by Western blot. Meanwhile, semi-quantitative RT-PCR was used to identify the gene expression profiles during the entire developmental period and in different tissues (testis, ovary, ganglion, head, silk gland, fat body, Malpighian tubules, midgut, hindgut, cuticle, blood, trachea) of the 5th instar day-3 larvae. 【Results】 A Sox family gene named BmDichaete (GenBank accession no.: KY914554) was cloned from B. mori, and its full-length cDNA sequence is 1 541 bp and the open reading frame is 741 bp, encoding a protein of 246 a.a. with an estimated molecular mass of 27.3 kD and pI of 9.89. The results of the homologous sequence alignment and phylogenetic analysis showed that BmDichaete has the typical HMG domain of the Sox family gene, and high homology with the Dichaete proteins of other lepidopteran insects. The expression profiling showed that BmDichaete possessed higher expression levels from the late stage of embryonic development to the early stage of pupation, while its expression level decreased in the late stage of pupation and adult stage. Moreover, BmDichaete was significantly overexpressed in the ovary, head, silk gland and hindgut. The expression characteristic analysis by Western blot indicated that BmDichaete was expressed continuously and steadily during the embryonic development of B. mori. 【Conclusion】 BmDichaete with the typical HMG domain should be classified into the Sox family. The BmDichaete gene plays a role in various stages of the embryonic development of silkworm. This study lays the foundation for the further research of the function of BmDichaete in the silkworm.