It’s the first time to modify cadmium sulfide (CdS) nanostructures using copper (Cu), yielding Cu-CdS, for oxytetracycline (OTC) removal and highly efficient hydrogen formation at the same time with dual cell. Cu-CdS composites were synthesized through photodeposition method. The high resolution transmission electron microscopy (HR-TEM) results reveal that Cu is uniformly loaded on the surface of CdS. Corresponding results show that the best Cu loading content for hydrogen production of 24.88 mmol h−1 g−1 is 1%. In addition, 4% Cu-CdS shows the best OTC removal efficiency of 81.4%. Moreover, H2 formation and OTC degradation is majorly induced by h+ and OH based on the results of scavenging experiment and electron paramagnetic resonance (EPR) analysis.