The CdS/Ti₃AlC₂ heterojunction photocatalyst was synthesized by the hydrothermal method, and its structure and performance were systematically analyzed through various characterization methods, including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS), and photoluminescence (PL) spectroscopy, etc. The results confirmed the successful construction of the composite material and its excellent charge separation ability. Under ultraviolet light irradiation, the photocatalytic degradation performance of tetracycline was studied, and its degradation mechanism was clarified, among which the superoxide radical (·O₂^-) was the main active species. Under the conditions of pH=7 and catalyst dosage of 0.1 g·L^-1, CdS/Ti₃AlC₂ exhibited excellent photocatalytic performance, with a TC degradation efficiency as high as 96.3%.