In order to obtain the influence of emulsion droplet size and distribution on the apparent viscosity and stability of heavy oil emulsion， the effect of temperature and shear rate on the average droplet size（referred to as droplet size）of Huanxiling heavy oil emulsion in Liaohe oilfield was investigated by using a focused beam reflectometer（FBRM） . The demulsification behavior of water-in-oil（W/O）emulsion after addition of alkaline viscosity reducer was dynamically monitored. The results showed that focused beam reflectometry enabled a good dynamic monitoring of the demulsification behavior of W/O emulsion and an assessment of the optimum amount of alkaline viscosity reducer. With increasing temperature， the droplet size of oil-water emulsion increased，and the viscosity of emulsion decreased. When the temperature was lower than 55℃ ，the droplet size of emulsion decreased with increasing shear rate， and the viscosity of emulsion decreased gradually. When the temperature was higher than 55℃， the shear rate had little effect on droplet size and viscosity of emulsion. After adding Na₂CO₃ solution to W/O emulsion，the emulsion emulsified in reverse phase， the viscosity of system reduced， the number of small size O/W emulsion droplets increased，the droplet size decreased， and the droplet distribution was more uniform. When the mass fraction of Na₂CO₃ was 0.2%， the viscosity of emulsion was the lowest， the droplet size of emulsion and the interfacial tension of oil and water reached the minimum.