A kind of latent curing agent for waterborne epoxy was synthesized using bisphenol A , formal-dehyde and dicyandiamide as monomers. The curing properties of the latent curing agent/epoxy E-51 were characterized by DTA. The stability and film property of the prepared water-borne epoxy emulsion were studied. Results show that the optimal content of curing agent is 45% and the curing temperature is 150℃ when epoxy resin was cured with the synthesized latent curing agent. The particle size of the water-based epoxy resin emulsion is about 0.38 μm and won’t delaminated at 3000r/min centrifugation for 30 min and has a storage period up to 6 months. It scured paints have good film properties.