In this study, S-doped graphitic carbon nitride (S-C₃N₄) was prepared using the high-temperature polymerization method, and then S-C₃N₄/AgCdS heterojunction photocatalyst was obtained using the chemical deposition method through loading Ag-doped CdS nanoparticles (AgCdS NPs) on the surface of S-C₃N₄. Experimental results show that the AgCdS NPs were evenly dispersed on the surface of S-C₃N₄, indicating that a good heterojunction structure was formed. Compared to S-C₃N₄, CdS, AgCdS and S-C₃N₄/CdS, the photocatalytic performance of S-C₃N₄/AgCdS has been significantly improved, and exhibits excellent photocatalytic degradation performance of Rhodamine B and methyl orange. The doping of Ag in collaboration with the construction of a Z-scheme heterojunction system promoted the effective separation and transport of the photogenerated carriers in S-C₃N₄/AgCdS, significantly accelerated its photocatalytic reaction process, and thus improved its photocatalytic performance.