Cadmium sulfide (CdS) is a vital wide-bandgap semiconductor that plays an important role in many fields. In this study, we grew CdS quantum dots on graphene oxide (GO) sheets using a novel chemical bath deposition approach. Highly reduced graphene oxide-CdS (rGO-CdS) nanocomposites were successfully obtained. H2S/N2 gas played a key role in the preparation of these nanocomposites, as it provided a source of S and reduced the GO. The size distribution and crystal structure of the CdS quantum dots and the reduction degree of GO in the rGO-CdS nanocomposites were investigated using various characterization techniques and the results showed that the GO was successfully reduced. Furthermore, CdS quantum dots (approximately 5–6 nm in size) with a hexagonal wurtzite structure were uniformly distributed on the rGO layers. The pollutant degradation performances of the rGO-CdS nanocomposites under visible light were studied, and the degradation mechanism was analyzed in detail. •Highly reduced rGO-CdS nanocomposites were successfully obtained.•H2S/N2 mixture gas provided S source and reduced GO.•The performance of rGO-CdS-2 exhibites the rapid photodegradation.•The degradation rate constant is ∼9 times higher than that of pure CdS.