Abstract: Visible-light responsive two-dimensional composite semiconductor materials are significant in the field of photocatalysis. Construction of stable and effective heterojunctions to promote interface charge transport is the key in the research of two-dimensional composite materials. In this work, a face-to-face stacked 2D-2D SnO₂/C₃N₄ composite semiconductor was synthesized by calcining carbon nitride (C₃N₄) nanosheets and SnO₂ nanosheets. The main structure of C₃N₄ and SnO₂ well stably retained and a stable heterojunction at the interface of them was formed. Photocatalytic test results of water splitting for hydrogen (H₂) evolution and active oxygen (O₂) for hydrogen peroxide (H₂O₂) generation show that under visible light irradiation, the composite sample of SnO₂/C₃N₄-5% while the content of SnO₂ is 5wt% shows much enhanced H₂ evolution activity (54.9 µmol·h⁻¹), which is about 2.1 times as that of C₃N₄ nanoseets. And the H₂O₂ generation activity of SnO₂/C₃N₄-5% is 78.9 µmol·L⁻¹·h⁻¹, which is about 11.9 times that of C₃N₄ nanosheets. The structural characterization and electrochemical tests show that the establishment of heterojunction facilitate the rapid transfer of photogenerated electrons from C₃N₄ to SnO₂, inhi-bite the recombination rate of excited electrons-holes, and greatly improve the photocatalytic reduction perfor-mance.