This disclosure relates to a method for preparing a polymer thin film with water repellency and oil repellency, including: thermally decomposing a thermal initiator to form a radical; reacting the radical with a monomer mixture of a specific composition to synthesize a polymer; and depositing the synthesized polymer on a substrate, and a polymer thin film with water repellency and oil repellency including a polymer resin including (meth)acrylate-based repeat units substituted with a fluorine-containing functional group and repeat units derived from a compound including at least two reactive functional groups at a specific ratio.