Herein, ZnO/CdS hierarchical composite was prepared through a hydrothermal and chemical bath deposition (CBD) process. Its photocatalytic H-2-production performance was tested. Mass ratio of CdS acted a pivotal part in light absorption and photocatalytic properties. Noticeably, promoted photocatalytic H-2-production activity of 4134 mu mol g(-1)h(-1) was achieved by the sample with optimal CdS content. Significantly, the photoluminescence (PL) detection of hydroxyl radicals, as well as the in-situ XPS measurements was selected to verify the direct Z-scheme charge migration mechanism. This mechanism endowed the composite with strong capability for hydrogen evolution and elucidated the improved photocatalytic performance. The improvement of photocatalytic activity was due to hierarchical structure, extended visible light response and direct Z-scheme mechanism. This work will give an innovative vision in constructing direct Z-scheme photocatalytic system with great photo catalytic H-2-production activity.