Abstract: The mechanism of rapid densification is one of the bases of the electro-induced effect in current-assisted sintering. This mechanism has been characterized as the effect of electric field intensity on the apparent (or diffusion) activation energy of sintering, and significant progress has been made. In this paper, the effects of applied electric field on the diffusion activation energy of crystal Cu are studied from two aspects of first-principles calculation and current-assisted sintering experiment. The results of the two studies reveal that the diffusion activation energy shows an obvious trend of regular decreasing trend under the action of electric field or current. In addition, to verify the positive correlation of the decreasing rule of two methods, current-assisted sintering experiment was conducted in which the inner diameter of the graphite die was varied to adjust the current density.