The development effects of heavy oil reservoirs after water flooding become poor due to the serious emulsification of produced liquid and reduction of formation fluidity in Block Jin17 of Shengli Oilfield. Therefore， the emulsification characteristics of heavy oil and water were studied through emulsification state analysis， viscosity， and rheology testing， oil-water interfacial tension （IFT） testing， etc.， and the flow characteristics of emulsified heavy oil were analyzed. Then， the re-emulsification characteristics of emulsified heavy oil were studied by analyzing the emulsification state， droplet size， viscosity， and viscoelasticity of emulsions formed by emulsification oil flooding agent and W/O emulsion. Finally， the re-emulsification mechanisms of emulsified heavy oil were analyzed， and the idea of emulsification oil flooding method was provided. The results show that emulsification has a serious effect on the viscosity of heavy oil emulsions. Under the reservoir temperature of 60 °C， the viscosity， viscosity modulus， and IFT of W/O emulsions with water content of 60% are 11.9，13.49，and 2.49 times that of dehydrated heavy oil， respectively. Moreover，the fluidity of W/O emulsions in the porous media is seriously restricted due to its stronger non-Newtonian characteristics， the viscosity increased exponentially， the viscous modulus increased significantly， and IFT increased rapidly when the water content is higher than 40%. W/O/W multiple emulsions are formed when emulsified heavy oil and emulsification oil flooding agents are reemulsified.Moreover， the droplet size， viscosity， and viscoelasticity of the emulsions increase with the increment of initial water content in W/O emulsion. When the initial water content of W/O emulsion is 60%，the droplet sizes of emulsions formed by emulsification oil flooding agents LPA， HPF， and SDS and W/O emulsion are 91.3，40.6， and 27.5 μm， respectively. Compared with the emulsions formed with dehydrated heavy oil， the droplet sizes are 7.9， 4.0， and 2.2 times， respectively. This indicates that the emulsification of formation water/injection water and heavy oil has a great influence on enhanced oil recovery of heavy oil by emulsification oil flooding agents. Therefore， strengthening the ability of emulsification oil flooding systems to penetrate oil film and replace the adsorption of active substances in heavy oil on the oil-water interface is the focus of subsequent research and development of emulsification oil flooding systems and construction method design.