Abstract: Effects of pulse frequency, pulse amplitude and pulse width ratio on the coalescence of water particles in W/O emulsions of Jilin Oilfield were investigated, which is helpful for understanding the mechanisms of high-frequency pulsed AC electrical fields on dehydration rate. The dehydration rate with the increase of pulse frequency increased and decreased, and 4.43 kHz was a peak, dehydration rate with the increase of pulse amplitude varied in a similar tendency, and 1320 V was a peak, dehydration rate increased with the increase of pulse width ratio whose maximum value was at 85%. Adding demulsifier to high-frequency pulsed AC electrical field made it easier to implement best demulsification with lower optimal pulse frequency and pulse width ratio, while the optimal pulse amplitude was not affected. The experimental results showed that under the conditions of dehydration temperature 55 ℃, duration time 10 min and 60 mg/L PR929 added, pulse frequency 3.86 kHz, pulse amplitude 1320 V, pulse width ratio 75%, the dehydration rate of the high-frequency pulsed AC electrical fields reached nearly 100%.