Abstract: Sox（SRY-related HMG-box）gene is a kind of important transcription factor, which functions in sex determination, organogenesis, etc. The gonad-specific expression of this novel gene suggested that it might play an important role in the development of gonad. To determine the exact role of EsSox21b-like gene using RNA interference, a EsSox21b-like-L4440 interference vector was successfully constructed for production of large amount of dsRNA. The target sequence of EsSox21b-like gene was inserted into the L4440 vector containing two T7 promoters. Then the recombinant plasmid was transformed into HT115 bacteria, a RNaseⅢ deficient strain. A large amount of EsSox21b-like sense and antisense RNAs was simultaneously transcripted in vivo when induced by IPTG. After denatured and annealed, EsSox21b-like double strand RNAs（dsRNAs）were produced and the yield of EsSox21b-like-dsRNA was enough for future RNA interference experiment on the role of EsSox21b-like gene.

Key words: Eriocheir sinensis, RNA interference, L4440, HT115, Prokaryotic expression, dsRNA