Abstract: The demulsification of water in oil(W/O)emulsion by freeze/thaw is a new physical demulsification method.By far, the demulsification process and mechanism are still unclear.By using a stable liquid paraffin emulsion as the object of study, the freeze/thaw demulsification process of W/O emulsion with a highly viscous continuous phase(oil phase) was studied with differential scanning calorimeter (DSC) and optical microscope.The results showed that the freeze/thaw demulsification was a gradual process.When the droplet was smaller than 5.5 μm, the emulsion system could be demulsified by several freeze/thaw cycles, and in the freeze/thaw cycles firstly the small droplets coalesced and grew, and then separated from the emulsion system.But when the droplet was larger, such as 51 μm, the demulsification would be complete only in one freeze/thaw cycle, with over 90%(vol) of demulsification ratio.In addition, it was found that the increase of water content was beneficial to demulsification efficiency.And it is the droplet size, not the water content affects the freezing point of water phase.When the droplet is larger, the freezing point temperature declines with the decrease of droplet size,the effect is not obvious when the droplet was smaller than 5.5 μm.