The widespread detection of antibiotics in aquatic environments has raised significant concerns due to their potential risks to human health. Photocatalytic technology has emerged as an effective approach for antibiotic degradation, with cadmium sulfide (CdS) being a promising semiconductor photocatalyst. However, the practical application of CdS is limited by its tendency to aggregate, which reduces the number of accessible active sites and consequently lowers its photocatalytic degradation efficiency. In this study, a series of GO/CdS composites were synthesized via a two-step hydrothermal method for the efficient degradation of tetracycline (TC) antibiotics in aquatic solutions. Results showed that GO/CdS can effectively remove TC via photocatalytic degradation rather than adsorption. The optimized photocatalytic composite achieved a 95% degradation of TC (20 mg L⁻¹) under 60 min of illumination. The corresponding rate constant (k) was 2.87 times higher than that of pristine CdS. After three cycles, the degradation rate still achieved 93%. Moreover, the composite exhibited a wide pH tolerance range from pH 2 to 10, with a removal rate of over 89%. Superoxide radicals (·O₂⁻) were identified as the primary reactive species responsible for TC degradation, and three possible TC degradation pathways were proposed. This work extends the application of GO and offers a novel strategy for constructing GO-based composite materials, providing valuable insights into the mechanisms and pathways of antibiotic degradation.