Electrocatalytic oxidation is a highly promising approach for degrading highly toxic phenol-containing pollutants. However, the catalyst-solution interface microenvironment induced by an anode electric field and its corresponding impact on degradation remain insufficiently understood. This study employs DFT methods to investigate the interfacial microenvironment and the degradation activity of 2,4,6-TCP on a Cu-N4/C catalyst under various electric fields. The results demonstrate that an anodic electric field increases the electrostatic potential of the Cu-N4/C substrate, creating a favorable microenvironment for dechlorination of 2,4,6-TCP. An optimized interfacial environment enhances charge transfer from 2,4,6-TCP to the substrate. The changed interface microenvironment also facilitates the degradation of 2,4,6-TCP on Cu-N4/C by lowering the free energy barriers of multiple key steps and altering the rate-determining step, and this degradation efficiency increases with the strength of the applied electric field. Additionally, AIMD simulations and binding energy calculations confirm that the Cu-N4/C catalyst remains structurally stable under electric field effects, indicating that the microenvironmental changes do not affect the durability of the catalyst. This research provides promising insights into the mechanism of interface microenvironment influence and holds potential to offer theoretical support for enhancing electrocatalytic performance in the future.