Abstract: The performance analysis of electro-desalting of several types of crude oil with high-salt and high-water content in atmospheric-vacuum distillation unit in Sinopec Maoming Company were conducted. The effects of critical factors on desalting, such as properties of crude oil, water injection, demulsifiers models, mixing intensity, temperature of desalting, and electric field strength, were analyzed. The results showed that pre-dewatering operation can be optimized by increasing the residence time of the crude oil in the oil tank, increasing the dehydration temperature and injecting demulsifier in the crude oil tank. Meanwhile, the problem of the dehydration outlet stream containing oil can be solved using the bidirectional demulsification and the optimization of the injection process. In addition, regularly clearing the oil spill in tank bottom, and optimizing the operational parameters can also improve the desalination effect.