The demulsification rates of water-in-crude oil emulsion in high AC fields were investigated under various conditions by using a model dehydrator. A continuous electrostatic dehydrator was constructed using a glass vessel of 6.5 cm diameter and 10 cm height equipped with a copper electrode and a perforated plate. The separation rate of water from the simulated crude oil increased along with the applied field, frequency, demulsifier concentration, temperature, and contact time. As the applied field increased up to 2.5 kV/cm, the separation percentage increased up to 90%, and as the concentration of the demulsifier reached 100 ppm, 80% of the water were separated at 2.5 kV/cm. Also it was observed that the separation percentage increased as the temperature, frequency of field, and contact time. It is proposed that the breakup of droplets depends on the interfacial polarization and the proper deformation of water droplets in the field induced by the electrostatic charge.