Abstract: Maltosyltrehalose synthase（MTSase） and maltosyltrehalose hydrolase（MTHase） are the key enzymes for enzymatic synthesis of trehalose. Due to the extremely low yield of this enzyme system in natural strains, researchers have successively expressed this enzyme system in various model microorganisms. In order to achieve the secretory expression of MTSase and MTHase in food-safe strains, this study chose the important industrial microorganism Bacillus licheniformis as the host strain. MTSase was used as the reporter protein. Through screening of natural promoters, it was found that P_P2 mediated the highest expression of MTSase. Based on the result of promoter engineering, a series of tandem promoters and synthetic promoters were constructed using promoter engineering. It was found that synthetic promoter P_1-P2 can increase the expression of MTSase by 37% on the basis of the original P_P2. This promoter also has an effect on the expression of MTHase. The expression of MTHase under the mediation of P_1-P2 is 10% higher than that under the mediation of P_P2. The enzyme activity of MTSase and MTHase in fermentation medium and P_1-P2 promoter could reached 6 907.9 U/mL and 798.5 U/mL, respectively.