In this work, we design and construct a novel 2D/2D g-C3N4 nanosheet@ZnIn2S4 nanoleaf via a simple one-step surfactant-assisted solvothermal method for photocatalytic H2 generation. Its unusual 2D/2D heterojunction structure provides far more contact areas and much faster charge transport rate than the 2D/OD heterojunction structure of g-C3N4 nanosheet@ZnIn2S4 microsphere. More importantly, this unique 2D/2D heterojunction leads the g-C3N4 nanosheet@ZnIn2S4 nanoleaf composite to generate numerous intimate high-speed charge transfer nanochannels in the interfacial junctions, and which could considerably enhance the photogenerated charge separation and migration efficiency, thus yielding a remarkable visible-light-driven H2 evolution rate without the additive Pt cocatalyst (HER = 2.78 mmol h(-1) g(-1)), nearly 69.5, 15.4, 8.2 and 1.9 times higher than that of pure g-C3N4 nanosheet, pure ZnIn2S4 microsphere, 2D/OD g-C3N4 nanosheet@Zitin2S4 microsphere and pure ZnIn2S4 nanoleaf, respectively. Additionally, the 2D/2D g-C3N4 nanosheet@ZnIn2S4 nanoleaf exhibits an outstanding stability and recyclability, manifesting a promising potential application in sustainable energy conversion. This work would provide a platform for the design and synthesis of binary heterojunction composite system with highly-efficient charge separation and transfer.