Abstract: In this paper, electrostatic demulsification and dehydration experiments were conducted on water-in-crudeoil emulsions with three kinds of water-cuts based on the independently established experimental system for electric-field demulsification and dehydration whose electric field parameters (waveforms especially) are adjustable. And the effects of electric-field waveform, frequency, voltage and water cut on demulsification characteristics of water-in-crude-oil emulsions were investigated systematically by taking dehydration rate and Turbiscan stability index (TSI) as the evaluation criterion. It is indicated that AC square wave is better at demulsification and dehydration than the sinusoidal wave, triangle wave and DC pulse wave. As to the high-frequency/high-voltage electical field with AC square wave, the optimum electrical frequency and electrical voltage vary slightly with water cut. The dehydration rate of water-in-crude-oil emulsions correspsonding to the optimum electric field parameters can be up to 98.7% when the water cut is 30%. When crude oil dehydration power unit is developed, AC square wave with high frequency/high voltage shall be adopted and upper limit of electric field frequency don't have to be too high. At the same time, TSI can be taken as a reliable quantitative index for evaluating the reasonable electric-field demulsification parameters.