［Objective］In order to solve the problems of waterborne epoxy emulsion，such as high VOC content，high amount of emulsifier and poor corrosion resistance of coating film under highpigment volume concentration（PVC）.［Methods］A high-efficiency emulsifier was synthesized by a specific process using dimer acid as modifier，which was then applied to prepare epoxy emulsions. Theproperties of emulsion and coating film were characterized by FT-IR spectrometer，laser particle size analyzer and differential scanning calorimetry.［Results］The prepared epoxy emulsion exhibited excellent stability. The coating under high PVC（46%）has excellent corrosion resistance，and the salt spray test exceeded 400 h with no blistering on the panel surface，and the unilateral corrosion expansionwas less than 2 mm. The emulsion particle size and fineness were optimized by adjusting the hydrophilic-lipophilic balance（HLB）and molecular weight of the emulsifier. The emulsion exhibited the best overallperformance when the dimer acid content was 14%.［Conclusion］ Compared with commerciallyavailable waterborne epoxy coatings，the dimeric acid modified epoxy emulsion coatings showed superior performance in terms of flexibility，hardness，impact resistance. Moreover，under the same PVC conditions，the corrosion resistance was significantly better than that of commercial available products.