In this research, the recombinant expression vector pBBR1gentaRhlAB containing the rhamnosyltransferase gene (RhlAB)was modified via Red/ET homologous recombineering. Then, three recombinant expression vectors pBBR1gentaPapraRhlAB，pBBR1kanPtacRhlAB and pBBR1kanPrhaBRhlAB with three different constitutive promoters (Papra、Ptac and PrhaB)were constructed by subcloning technology，and then we electrotransformated the resultant expression vectors into P.protegens Pf5．When the flask in LB medium was fermented to 42 h, the rhamnolipid concentration of Pf5/pBBR1gentaRhlAB supernatant was 17.56 mg/L, with that of Pf5/pBBR1gentaPapraRhlAB, Pf5/pBBR1kanPtacRhlAB and Pf5/pBBR1kanPrhaBRhlAB supernatant being 11.135 mg/L, 441.135 mg/L and 557.764 mg/L, resulting in 0.63，25.12 and 31.76 fold variation after promoter optimization. High performance liquid chromatographymass spectrometry (LCMS/MS)analysis showed that there were total 4 rhamnolipid derivatives in the Pf5 engineering bacteria. Furthermore, the RhlAB gene expression was later examined by qRTPCR with the result showed that the expression level of RhlAB gene after Ptac and PrhaB promoter was 2.16 and 2.77 fold higher than that of the original one. Generally, this study preliminarily realized the expression of RhlAB gene in Pf5, and found that the constitutive promoter Ptac and PrhaB was more efficient than the original promoter which could provide a significant reference  with significance for heterologous biosynthesis of rhamnolipid.