The present invention relates to a pharmaceutical composition for treating liver diseases, comprising a miRNA mimic containing a single strand RNA molecule of hsa-miR-21-3p (SEQ ID No: 35). The miRNA mimic of the present invention can be used to treat liver diseases through regulating the expression of methionine adenosyltransferase 2A and 2B (MAT2A and MAT2B), acetyl-CoA carboxylase 1 and 2 (ACACA and ACACB), diglyceride acyltransferase 2 (DGAT2), and so on. In addition, the present invention also relates to a method for reducing the expression of the above-mentioned enzymes.
