As a potential environmental pollution control and clean energy synthesis technology, photocatalysis has attracted enormous attention of scientists, researchers, and innovators. However, conventional photocatalysts have encountered a lot of issues in solar light utilization and photocatalytic capability. Here, we proposed a solution by decorating narrow‐bandgap In2S3 nanosheets on sheet‐like g‐C3N4 to form a Z‐schemed photocatalyst to realize visible light utilization without sacrificing its photocatalytic capability. The composite was used to split water under visible light. Our results show that such a Z‐schemed photocatalyst has excellent photocatalytic activity in H2 evolution, which exhibited an H2 generation rate up to 307 μmol g−1 h−1 under 300 W Xe lamp illustration. The favorable performance benefits from the effective solar light absorption by the narrow‐bandgap components, In2S3 and g‐C3N4. The unique photocarriers transfer behavior in such a Z‐scheme structure will respond to its high photocatalytic capability. The work finds new ideas to achieve high‐performance photocatalysts by rationally designing their material architecture and energy band structure.