As is known, once forming stem-loops, the oligonucleotides will be more stable than the single-stranded ones. And mRNA with stem-loop at its 3’ or 5’ end often get a longer lifetime than the linear one owe to the stem-loop’s resistance to exonuclease. Our team tend to design a series of stem-loops each followed by the same endonuclease site and are transcribed as one polycistron. Once digested by endonuclease and seperate into several independent fragments, cistrons with different ∆G stem-loops will get different stability, thus influence the amount of expressed proteins. In this way, we can decouple the expression level of upstream and downstream genes of the same operon by simply designing different stem-loops. Futhermore, with quantitative ∆G of stem-loops, we even can achieve the ratio expression of target proteins. It is a creative regulating method and we attempt to provide a series of standard regulation parts for others.