［Objective］To address the issue of high brittleness and poor toughness of bisphenol-A epoxy resin after curing.［Methods］ The reaction products of phthalic anhydride with 1，4-butanediol，1，6-hexanediol，and 1，10-decanediol were used as dicarboxylic acids to modify bisphenol A epoxy resin E51，which were then phase-transferred and emulsified to prepare the correspondingmodified waterborne epoxy resin（PE）. At the same time，bisphenol A was used to replace thedicarboxylic acids to prepare a BPA-type waterborne epoxy emulsion（PEB）as a comparison sample. The structure of the products were characterized by nuclear magnetic resonance（NMR） proton spectroscopy and infrared（IR）spectroscopy. The glass transition temperature（T_g）of the PE and PEB resins and the thermodynamic properties of their cured films were characterized using differential scanning calorimetry（DSC）and dynamic mechanical analysis（DMA）. In addition，waterborne epoxy primers were prepared by mixing PE and PEB with amine curing agents，and the application performance of the primers was studied.［Results］The T_g of PE resins were significantly lower than that of PEB；the thermodynamic properties of the cured PE films were clearly influenced by thestructure of the diol，with the PE-6 film prepared using 1，6-hexanediol showing significantly improved tensile strength and elongation at break，making it stronger and tougher than the PEB cured film. The PE-6 primer demonstrated the best mechanical and chemical resistance properties，comparable to the PEB primer，and superior impact resistance.［Conclusion］In summary，through molecular structure design，the strength，toughness，and storage stability of waterborne epoxy resins could be synergistically optimized，providing a new strategy for efficient toughening of waterborne epoxy resins.