A simple two-step hydrothermal method synthesized four different CdS/Fe₃O₄ photocatalysts with varying ratios of mass of CdS to Fe₃O₄. The composition and morphology of the prepared samples were investigated using X-ray diffraction (XRD), Raman spectrum, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Solid UV reflectance spectra testing found that CdS/Fe₃O₄ nanocomposites had good light absorption throughout the spectral range, promoting their photocatalytic properties. Under visible light irradiation, CdS/Fe₃O₄ (2:5) with a mass ratio of 2:5 exhibited excellent photocatalytic performance, with a degradation rate of 98.8% for rhodamine B. Furthermore, after five cycles of photocatalytic degradation reaction, the rhodamine B degradation rate remained at 96.2%, indicating that the photocatalysts have good photocatalytic stability.