Introducing structural distortion to semiconductors can dramatically modify their electronic structures, resulting in efficient separation of electron-hole pairs and achieving high photocatalytic activity of catalysts. Herein, we systematically studied the role that structural distortion played in the photocatalytic process by taking graphitic-C3N4 (g-C3N4) as an example, where the structural distortion can be introduced by elemental doping and heat treatment. Through the controllable structural distortion engineering, the photocatalytic activity of g-C3N4 can be significantly improved, which benefits from the effective separation of photogenerated electron-hole pairs, showing intriguing structural distortion-dependent photocatalytic activity. This study not only offers a new insight into the in-depth understanding of the effect of structural distortion on the photoreactivity of catalysts, but also provides a new pathway for designing advanced photocatalysts.