A technology of ultrasonic-electric united desalting and dewatering of crude oil is studied. The ultrasonic setup is designed to form a standing-wave field, which is more efficient for agglomeration of water particles. The desalting and dewatering, results of the ultrasonic-electric united process are compared with those of the electric process. For high salt-contenting crude oil (40-70 mg center dot L-1), the salt content is still above 10.0 mg center dot L-1 after crude oil has been treated by two-stage electric desalting process in refinery. which cannot meet the need of refinery. Ultrasonic-electric united process is a novel technology for treating the high salt-contenting oil. On the optimal operating conditions of the ultrasonic-electric united process, the salt content of crude oil can be reduced from 67.5 mg center dot L-1 to 3.97 mg center dot L-1 by one-stage ultrasonic-electric united process, and the water content falls below 0.3% (by mg center dot L-1 volume). The results show that the ultrasonic-electric united process is more effective than the electric process in high salt-contenting oil desalting. This technology should be useful in the refinery process.