We have compared high water content crude oil of Daqing Oilfield with the demulsifier GP or C. the optimized demulsifier of GP and C can improve the dewatering speed in room experiments. Using the crude oil of different water content ratio, the dewatering time is between 30min and 60min and the dewatering ratio is above 97%. The higher of water content , the higher the dewatering speed and the higher the dewatering ratio. Using the optimized demulsifier, the demulsified temperature decreases from 55 ℃ to 40℃. It can save production cost. The dewatering ratio of optimized demulsifier is high and water content ratio of export crude oil is about 0. 20%, meeting the export standard.