Abstract: Heavy oil demulsifier SLDE - 01with low temperature and high effective performances has been developed according to the characteristic of large viscosity and high colloid content of crude oil of Gudong No. 4 combination station in Shengli oilfield. This agent is propene polyoxy-ethylene binary block polyether chain extension production initiated by polyamine and polyalcohol. The indoor experiment and its application at site showed that This oil - soluble demulsifier has high dehydrating rate, neat oil/water interfaces and clean separated water which can lower dehydration temperature by 10℃and the newly developed demulsifier SLDE-01 is excellent in comparison with the water- soluble demulsifier used presently in the oilfields, which can increase dehydration efficiency, save lager amount of energy,and reduce production cost of crude oil.