Abstract: A Ce-Ag₃PO₄/TCPP heterojunction composite catalyst was constructed by combining with 5, 10, 15, 20-tetra (4-carboxylphenyl) porphyrin (TCPP) to investigate its catalytic degradation performance for Spiramycin (SPM). Using SEM, XRD, XPS, UV-Vis DRS and FTIR methods to characterize and analyze the microchemical structure, chemical composition and photochemical properties of the catalysts and further clarify the reaction mechanism of SPM photocatalytic degradation. The Ce-Ag₃PO₄/TCPP photocatalyst has a degradation ratio of 87.7% for SPM under visible light irradiation for 6 h, and the degradation rate constant is 5.8 times that of pure Ag₃PO₄. Photoelectrochemical measurements (photocurrent response, electrochemical impedance), ESR test, radical trapping, and PL spectral analysis results show that the doping of cerium ions (Ce³⁺) can effectively increase the specific surface area of the catalyst and reduce the recombination of electron-hole pairs; the introduction of TCPP can accelerate electron transfer and enhance light absorption performance, thereby enhancing the photocatalytic activity. This doped composite catalyst provides a simple and efficient route for efficient photodegradation of SPM.