Abstract: An ultrasonic demulsification technology has been studied in laboratory to intensify dewatering for the 20%-30% water-content waste oil from Sinopec Yangzi Petroleum & Chemical Co.The ultrasonic parameters are examined for waste oil dewatering with 20 kHz ultrasound.The results show that under the ultrasonic irradiation time of 5min,ultrasonic exciting voltage of 100V,settling temperature of 60℃ and settling time of 2h,the water content can be reduced to 3.2% in a small scale test.Middle-sized scale experimental results show that the water content as expected can be reduced to 7.2% with the parameters used in the small scale experiments.