Abstract: To address the issue of water pollution caused by the organic dye Rhodamine B (RhB), a S-scheme P-doped g-C₃N₄/MoS₂ (PCN/MoS₂) heterojunction photocatalyst was fabricated via secondary thermal method by combining molybdenum disulfide (MoS₂) at different mass ratios with P-doped g-C₃N₄. The structure, morphology, optical and electrochemical properties of the catalysts were systematically characterized by means of XRD, SEM, XPS, PL, UV-Vis, and photoelectrochemical tests, revealing a S-scheme mechanism whereby P doping and MoS₂ composite synergistically promote the separation of photogenerated carriers. The photocatalytic performance was evaluated using RhB as a model pollutant. Results show that PCN/MoS₂0.4% achieved a degradation rate of 94.78% within 3 hours under visible light, with first-order kinetic constants 1.54 and 2.78 times those of PCN and CN, respectively. After five recycling tests, the degradation rate decreased by only 3.27%, demonstrating excellent catalytic activity and stability.