The invention discloses an antibacterial styrene-acrylic emulsion, and a preparation method and the application thereof. The emulsion is prepared from the following components in parts by weight: 40 to 60 parts of deionized water, 15 to 20 parts of styrene, 15 to 20 parts of butyl acrylate, 3 to 5 parts of an emulsifier, 1 to 2 parts of a water-soluble initiator, 0.5 to 1 part of an oxidation-reduction system initiator, 2 to 7 parts of an antibacterial monomer, 0.1 to 0.3 part of a pH value regulator and 3 to 5 parts of other auxiliaries. By taking a main measure of adding a monomer having the antibacterial function for participation in polymerization reaction during synthesis of the styrene-acrylic emulsion, the styrene-acrylic emulsion has an antibacterial function, and no antibacterial auxiliary is needed; moreover, the styrene-acrylic emulsion is uniform in dispersion and difficult to seep. The antibacterial styrene-acrylic emulsion has the characteristics that the styrene-acrylic emulsion is high in efficiency and low in toxicity, is hardly affected by the change of the pH value, and is convenient to use, has a relatively strong stripping function for a mucous layer, is stable in chemical property, and has relatively good dispersion and corrosion inhibition effects.