Strong interfacial electric field can promote the separation and transfer of photogenerated carriers of photocatalysts. Herein, a three-dimensional (3D) network structure assembled from carbon-coated C 3 N 4 nanowires (denoted as 3D C 3 N 4 @C) with a giant interfacial electric field was prepared. The unique 3D structure works with the carbon layer to expand the light absorption range of C 3 N 4 to the full spectrum. Under visible-light irradiation (λ≥420 nm), the degradation rate constants of 3D C 3 N 4 @C for bisphenol A and phenol were 41.2 and 5.7 times that of bulk g-C 3 N 4 , respectively. Meanwhile, the interfacial electric field of 3D C 3 N 4 @C-2mol/L was 5.14 times that of bulk g-C 3 N 4 . The charge transfer process of 3D C 3 N 4 @C was confirmed by synchronous illumination X-ray photoelectron spectroscopy and DFT. The significantly improved activity was mainly ascribed to the giant interfacial electric field between g-C 3 N 4 and the carbon layer, which significantly promoted the separation and transportation of photo-generated charge carriers. • Three-dimensional (3D) network structure assembled by carbon-coated C 3 N 4 nanowires was prepared. • The giant interfacial electric field between g-C 3 N 4 and carbon, as well as the synergy between the unique 3D structure and the carbon coating, improve the photocatalytic performance and light absorption. • The rate constants of 3D C 3 N 4 @C-xmol/L for bisphenol A and phenol degradation were 41.2 times and 5.7 times higher than those of g-C 3 N 4 , respectively.