Abstract: The semiconductor photocatalysis are considered as one of the most promising candidates in hydrogen energy source and environmental remediation area. In this paper, flower-shaped SnS₂ is successfully combined on g-C₃N₅, and the well matching band structure successfully constitutes a new Type-II heterojunction. As expected, the photocatalytic hydrogen production experiment showed that the quantity of hydrogen produced on 5% SnS₂/C₃N₅ was 922.5 μmol/(h·g), which is 3.6 times higher than that of pure g-C₃N₅. Meanwhile, in photocatalytic degradation of methylene blue, 5% SnS₂/C₃N₅ composite material can degrade 95% of contaminants within 40 minutes, showing good photocatalytic degradation performance. The mechanism study indicates that SnS₂/C₃N₅ heterojunction improves the photogenerated charge migration rate and reduces the electron-hole recombination rate, and effectively improves the photocatalytic performance of g-C₃N₅. This work provides a new idea for designing C₃N₅-based heterojunctions with efficient hydrogen production and degradation performance.