Disclosed are a new type of nucleic acid unit for the construction of a polymeric nucleic acid and a polymeric nucleic acid for interfering with target gene expression. In the present invention, by means of the design and construction of the new type of nucleic acid unit and the self-assembled polymeric nucleic acid thereof, multiple target interference can be realized, wherein same can be used for inhibiting multiple gene expression in the signaling pathway of disease occurrence or development, or simultaneously inhibiting multiple disease target gene expressions, possessing broad application prospects in multiple subject areas such as biology and chemistry, etc. The polymeric nucleic acid can target multiple sequences simultaneously, wherein the sequences may be located in one or more genes. The advantages of the present invention comprise: 1) a high RNAi performance； 2) good stability； 3) reduction of the off-target rate； 4) enhanced ability to be introduced into cells； and 5) a modular design.
