The invention relates to a promoter sequence capable of specifically responding to an osmotic stress signal so as to further activate expression of a target gene. Four recombinant expression bacterial strains are obtained by constructing a fusion expression vector of the promoter and respectively transferring the expression vector to nitrogen-fixing pseudomonas stutzeri as well as three industrial microbial fermenting bacterial strains: escherichia coli, bacillus thuringiensis and corynebacterium glutamicum. Experiments verify that compared to a non-stress condition, under the osmotic stress condition, the promoter provided by the invention can be used for specifically and efficiently starting expression of the targeted gene in the four bacterial strains. Therefore, the promoter has application value in microbial fermentation and genetic engineering fields.