The invention discloses preparation and application of a short-chain fluorine-containing copolymer water-repellent oil-repellent finishing agent. A preparation method of the finishing agent comprisesthe following steps: taking short-carbon-chain perfluoroalkyl group acrylate, non-fluorine-containing acrylate monomer, and cross-linking monomer, emulsifying the monomers under the effect of a cationand nonionic compound emulsifier, further finely emulsifying by virtue of a homogenizing machine or in an ultrasonic environment, finally dropwise adding a water-soluble initiator, initiating the polymerization, and preparing a short-chain fluorine-containing copolymer fine emulsion. By adopting the fine emulsion polymerization method in the preparation process, no organic solvent is needed, andthe stability of the copolymer emulsion is ensured; and in addition, by utilizing a short-chain fluorine-containing chain segment with a carbon chain number smaller than 6, while the excellent water-repellent and oil-repellent performance is ensured, the environmental protection requirement can be met.