The present invention discloses a liposome formulation, its preparation method, and its application in the treatment of diseases caused by abnormal gene expression. The liposome formulation comprises complementary cationic lipid pairs, phospholipids, and long-circulating lipids. The method of preparing the liposome formulation comprises: mixing the complementary cationic lipid pairs with the phospholipid and the long-circulating lipid to generate pre-formed vesicles and then mixing the pre-formed vesicles with the nucleic acid solution to generate the liposome-nucleic acid formulation. This liposome formulation provided by the present invention is easily prepared and in the treatment of diseases caused by abnormal gene expression, the liposome formulation can be used to deliver in vivo therapeutic agents, including nucleic acids.
