Abstract: Electric field treatment is a new method to improve the cold flowability of waxy crude oil. Its basic principle is electrorheological behaviors of waxy oil, and its mechanism is the interfacial polarization of wax particles. So far, researchers have found that the effect of electric field treatment varies greatly among different crude oils, yet the mechanism is unclear. Herein, the effect of electric field treatment on improving flowability was tested using 8 waxy crude oils with various resin and asphaltene contents ranging within 4% to 23%. The results show that: under the experimental conditions, the crude oils with lower resin and asphaltene content (of which the total mass fraction is less than 5%) have the viscosity reduction effect induced by electric field increase first and then decrease with the increasing of cumulative amount of wax precipitated; the crude oils with medium resin and asphaltene content (of which the total mass fraction is about 10%) have the viscosity reduction effect induced by electric field increase monotonically with the increasing of precipitated wax; the crude oils with high resin and asphaltene content (of which the total mass fraction is above 15%) have unobvious viscosity reduction effect induced by electric field. It is concluded according to the mechanism of interfacial polarization of wax crystal particles of flowability improvement by electric field treatment is closely related to the abundance and aggregation degree of rein and asphaltene in crude oil.