The invention discloses a modified epoxy resin emulsion, and a preparation method and an application thereof. The preparation method comprises the following steps: heating a mixed reaction system containing N,N,N',N'-tetramethyl-1,6-hexanediamine, a bisphenol A epoxy resin and an organic solvent to perform react a reaction, adjusting the obtained reaction mixture to be neutral or weakly acidic, and adding water to obtain the modified epoxy resin emulsion. The modified epoxy resin emulsion has the advantages of excellent stability, simple preparation method, long-term storage without deterioration, small influences on the environment, and easiness in dissolving and dispersing in the coating preparation process; and the preparation method is simple, so batch production is facilitated, and the problems of non-uniform dispersion and serious sedimentation of a pigment and filler when a traditional epoxy resin is used as a film-forming substance are solved. A conductive coating prepared fromthe modified epoxy resin emulsion has a lasting conductivity, can slow down or prevent damage to a metal matrix, and can be applied to protection of grounding grid metals under different working conditions.