NOVELTY - Polyether type heavy oil low temperature demulsifier is prepared by reacting glycerin and powder sodium hydroxide in acetic acid and in presence of catalyst at 250-260 degrees C, adjusting pH value of polyglycerol product to 7, separating and purifying to obtain polyglycerol; adding polyglycerol and alkali metal hydroxide catalyst, then continuously adding propylene oxide and reacting at 110-140 degrees C for 15-60 minutes to obtain polyether product; and reacting polyether product and isocyanate in aromatic hydrocarbon solvent at 70-80 degrees C for 6 hours to obtain the oil demulsifier.    USE - Method of preparing polyether type heavy oil low temperature demulsifier (claimed).    ADVANTAGE - The method utilizes by-product glycerin from biological diesel oil production as raw material to replace ethylene oxide as polyether emulsion splitter; has low cost of raw material and good effect on heavy oil emulsion breaking; and is safe to use. Further, the method can greatly improve glycerin utilization rate so as to promote development of biodiesel industry.    DETAILED DESCRIPTION - Preparation of polyether type heavy oil low temperature demulsifier comprises:    (A) adding glycerin (100-200 g) and powder sodium hydroxide (3-6 g) into a four-mouthed flask equipped with water separator, thermometer, and stirrer, introducing nitrogen gas and raising temperature to 250-260 degrees C, monitoring polyglycerol refractive index, controlling degree of polymerization of polyglycerol to 2-12, after the reaction is finished, vacuumizing at 133.3 KPa for 0.5-1 hour, reducing temperature to 90-100 degrees C, adding acetic acid and catalyst, adjusting pH value of polyglycerol product to 7, separating and purifying to obtain polyglycerol;    (B) adding polyglycerol and alkali metal hydroxide catalyst into a high pressure reaction kettle with stirring, then continuously adding propylene oxide into the reaction kettle, controlling reaction kettle pressure to 0.2-0.4 MPa and reacting at 110-140 degrees C for 15-60 minutes until the pressure does not change to obtain polyether product; and    (C) adding polyether product and aromatic hydrocarbon solvent in a reactor with stirring, keeping reaction temperature to 50 degrees C, then dropping isocyanate for 20-40 minutes, after dropping raising temperature to 70-80 degrees C, and keeping the reaction for 6 hours to obtain the oil demulsifier.