A novel Ag4V2O7/g-C3N4 heterostructure was synthesized by a facial etching method in ammonia solution using Ag2VO2PO4/g-C3N4 as a self-sacrifice precursor. With the concentration of ammonia solution increasing from 0.05 to 0.2 M, phase transformation took place, described as: Ag2VO2PO4/g-C3N4 Ag2VO2PO4/Ag4V2O7/g-C3N4 Ag4V2O7/g-C3N4. Compared with pristine Ag2VO2PO4/g-C3N4, the etched samples of Ag4V2O7/g-C3N4 and Ag2VO2PO4/Ag4V2O7/g-C3N4 exhibited dramatically improved activity for the degradation of methylene blue (MB), methyl orange (MO) and imidacloprid under visible light irradiation. When etched with 0.15 M ammonia solution, an Ag4V2O7/g-C3N4 heterostructure was obtained that exhibited the highest photoactivity. This photocatalyst was nearly 9.1, 3.0, and 24.3 times more efficient than pristine Ag2VO2PO4/g-C3N4 for degradation of MB, MO and imidacloprid, respectively. The excellent photocatalytic performance can be ascribed to the as-obtained well-defined Ag4V2O7/g-C3N4 heterojunction, which improves the separation and transfer efficiency and prolongs the lifetime of photoinduced charges. In addition, the stability and dominant radicals were investigated.