Charge separation is generally considered as the most critical step to achieve efficient photocatalytic reactions. Although charge separation can be promoted by a semiconductor heterojunction, its efficacy is inherently restrained by the mismatched atomic arrangements across the heterojunction interfaces. Here, Ta₃N₅-LaTaON₂ heterojunction with matched interfaces has been fabricated by one-step ammonolysis treatment of KLaTa₂O₇. The match interfaces are formed by nearly perfect adhesion of Ta₃N₅ (010) and LaTaON₂ (10$\overline{1}$) facets whose interatomic distance is similar. Compared with conventional heterojunction, the so-formed Ta₃N₅-LaTaON₂ heterojunction are extremely efficient in accelerating charge separation which in turn enables a high photocatalytic activity. An apparent quantum efficiency as high as 11.6% at 420 ± 20 nm has been reached by Ta₃N₅-LaTaON₂ heterojunction, which is almost three times higher than Ta₃N₅/LaTaON₂ mixtures. These results signify the importance of matched heterojunction interfaces for charge separation and provide a paradigm in the design of efficient heterojunction-based semiconductor photocatalysts.