The invention discloses single-component aqueous epoxy resin emulsion capable of being self-cured at normal temperature, and a preparation method thereof. The method comprises the following steps of: adding epoxy resin, n-butyl alcohol, and ethylene glycol monobutyl ether into a reactor, heating to form a homogeneous phase, controlling temperature to be 110 to 120 DEG C, and dripping acrylic ester monomers in which initiator benzoyl peroxide (BPO) is dissolved to obtain an acrylic ester monomer modified epoxy resin; and heating the acrylic ester monomer modified epoxy resin to 120 to 150 DEG C, adding unitary unsaturated fatty acid and catalyst triphenylphosphorus, adding maleic anhydride, reacting for 1.0 to 2.0 hours, reducing temperature to 50 to 55 DEG C, adding triethylamine, neutralizing for 0.5 to 1.0 hour, adding water and dispersing for 0.5 to 1.0 hour to obtain the single-component aqueous epoxy resin emulsion capable of being self-cured at normal temperature. The aqueous epoxy resin emulsion which is obtained by the method can be cured at normal temperature to form a film under the condition of not adding a curing agent, is convenient to use, and high in water resistance and corrosion resistance, and can be used for metal corrosion-resistant paint and the like.