Semiconductors are promising photocatalysts for the use of sunlight in energy conversion and environmental remediation. To this end, various synthetic pathways have been proposed to increase their photocatalytic efficiency, catalytic stability, recycle, and reuse. In this work, mixed phase CdS nanoparticles were loaded on the surface of activated biomass carbons to prepare composite photocatalysts via hydrothermal syntheses, which were further applied to photocatalytic degradation of rhodamine B (RhB) under visible irradiation. The composite photocatalysts displayed considerable specific surface area (up to 672 m g) and suitable band gap energy of ca. 2.1 eV. Due to the excellent light adsorption ability and chemical stability, these composite photocatalysts exhibited excellent photocatalytic capacity toward RhB degradation under visible irradiation. Moreover, the photocatalytic stability was also demonstrated by cyclic experiments, by which the composite photocatalysts retained over 80% of the initial catalytic activity after 4 consecutive runs.