Abstract: Photocatalytic H₂O₂ production has attracted much attention due to its green and sustainable advantages, in which constructing an efficient photocatalyst is the key. As a new semiconductor material, g-C₃N₄ has the advantages of good thermal stability, chemical stability and visible light response ability. Therefore, g-C₃N₄ has gradually become a research hotspot in the field of photocatalysis. In this paper, NiS/g-C₃N₄ is successfully prepared NiS/g-C₃N₄ by impregnation method, and the characterization indicates that the introduction of NiS increases the reactive sites of g-C₃N₄ and constructs abundant charge transport channels, which is conducive to the migration and separation of photogenerated carriers at the interface. The synthesized NiS/g-C₃N₄ was used for the photocatalytic H₂O₂ production under visible light without the introduction of additional sacrificial agents. The results show that H₂O₂ yield of NiS/g-C₃N₄ (3%) can reach 141.81 μM in 120 min, which is 3.8 times higher than that of bulk g-C₃N₄.The stability of the prepared samples was investigated by cycling experiments of photocatalytic H₂O₂ production. The trapping agent experiment of the active group in the photocatalytic hydrogen peroxide production is carried out. Based on the analysis of the results, the possible photocatalytic mechanism of the photocatalytic hydrogen peroxide production by NiS/g-C₃N₄ heterojunction is proposed.