In this study, facile solid-state CdS quantum dots (QDs) supported MoO3/g-C3N4 nanostructure photocatalysts were prepared via an innovative in-situ deposition protocol with consecutive ionic layer adsorption and reaction. The CdS QDs-anchored MoO3/g-C3N4 heterostructure photocatalysts demonstrated enhanced visible-light absorption capacity, which was realized by the quantum confinement of the CdS QDs. The maximum photocatalytic hydrogen (H2) production rate with the CdS QDs-anchored MoO3/g-C3N4 heterostructure photocatalysts reached 294.32 μmol g− 1 h−1, which was 76.84, 215.21, 27.12, and 3.64 folds superior as compare to bare g-C3N4, MoO3, CdS, and MoO3/g-C3N4 catalysts, respectively. The enriched photocatalytic performance was mainly credited to the high surface area and MoO3 with oxygen vacancies (OV), ultra-thin g-C3N4 and high optical adsorption ability of CdS QDs. Thus, forming a dual Z-scheme system in the CdS QDs-supported MoO3-OV/g-C3N4 nanostructures not only facilitated efficient interfacial charge transfer but also preserved the robust redox ability of the photoinduced electrons and holes.