We previously isolated 9 clones that show stronger signal compared to B. mori cytoplasmic action gene(BmA3) by using a dot blot hybridization. In this study, we focused on one clone among these clones which has high amino acid homology with elongation factor α gene of B. mori. This clone, named bEF1α(B. mori elongation factor α) was ubiquitously expressed in all tissues and developmental stage of B. mori. As result of promoter assay using dual luciferase assay system, we found the highest transcription activity region (-702/+38) in the 5`-flangking region of bEF1α gene, which has about 20 fold more intensive promoter activity than BmA3 promoter. Moreover, the bEF1α promoter was normally regulated in Bm5, Sf9, and S2 cells. Therefore, we suggest that bEF1α promoter may be used more powerful and effectively for transgene expression in various insects containing B. mori as a universal promoter.