Clusters with this unique atomic arrangement and configuration are highly potential cocatalysts, but designing efficient clusters and clarifying the mechanism of action remains a challenge. Herein, CoS clusters are in-situ grown on CdS nanorods, which leads to the existence of Cd-S-Co bonds. It is found that the Cd-S-Co bonds could induce interfacial charge rearrangements. Theoretical calculations reveal that the charge redistribution of heterostructures at interfaces is conducive to modulating d-band center, reducing thermodynamic energy barriers, and improving carrier separation. The optimized CdS/CoS composite shows a great photocatalytic H2 production rate (65.7 mmol h−1 g−1), such a H2 evolution rate exceeded most reported CdS nanorods photocatalyst. This study provides an experimental and theoretical foundation for the preparation of cluster-semiconductors photocatalytic materials and explores the transfer pathway between clusters and catalysts at the atomic level, and deeply discusses the mechanism of their catalytic performance.