Using the OP⁃10 and L61 emulsifiers to configure different hydrophilic equilibrium values (referred to as the HLB),the viscosity test of heavy oil in the second area of the oil production plant of liaohe oilfield was carried out to find out the optimal HLB of the heavy oil.At the same time, FBRM was used to measure the viscosity of heavy oil, and the effect of droplet quantity and particle size on viscous oil viscosity was analyzed.For further study on the viscosity change mechanism of heavy oil emulsion, it can be used to provide reference for the process of heavy oil reduction.Test results show that:the HLB of the emulsifying agent added to the heavy oil emulsion was 9.0,the effect of viscosity is best.At this time, the number of droplet drops to stable, compared with other HLB emulsifiers, the quantity of emulsifier is obviously low, the droplet is evenly distributed and the emulsion is stable.