Abstract: Dehydration of produced fluid from the heavy oil reservoirs in Henan oilfield is difficult, due to large viscosity and high colloid content of the heavy oil. Although increasing dehydration temperature can meet the requirements of demulsification and dehydration, it not only causes loss of large amount of thermal energy, but also imposes heavy operation load to the system, which influences the operation safety of the system. A new low temperature demulsifier is developed and applied. It can lower dehydration temperature of crude oil, increase dehydration efficiency, save large amount of energy, and improve the system stability.