Abstract: In order to explore the actual change in the particle size distribution of the dispersed phase water droplets of the water-in-oil emulsion in the electric field demulsification process, and obtain the optimal electric field parameters according to the change rules of the particle sizes, a dynamic test evaluation system for high-voltage electric field demulsification was set up with a self-developed compact tubular high-voltage electric field coalescer, a G600 focused beam reflectance measurement instrument and a high-frequency/high-voltage pulsed AC power supply. On the basis of testing and verifying the effectiveness of the evaluation system, tests of evaluation for the impact of the electric field intensity, frequency, duty cycle and water content on the performance of the compact tubular high-voltage electric field coalescer were conducted systematically. The test results indicate that: for the prepared white oil emulsion with a water content of 30%, the optimal combination of electric field parameters for demulsification comprises an electric field intensity of 1.2 kV/cm, a frequency of 1 500 Hz and a duty cycle of 45%. With the water content of the white oil emulsion changed to 20% and 40% successively, the optimal electric field intensities obtained are 1.65 kV/cm and 1.05 kV/cm, and the optimal frequencies are 2 000 Hz and 1 500 Hz respectively, which indicates that the optimal electric field intensity decreases gradually with the water content of the emulsion increasing. Meanwhile, the optimal frequency also presents a trend of decreasing. The self-developed test evaluation system and the evaluation method for high-voltage electric field demulsification can accurately and effectively characterize the change rules of the particles size distribution of the dispersed phase in the emulsion.