Using citric acid as a chelating agent, BiFeO₃ nanopowders doped with La at the A-site, Mn at the B-site, and co-doped with La/Mn were synthesized through an ultrasonic-assisted sol-gel method. Characterization techniques such as X-ray diffraction (XRD), ultraviolet visible diffuse reflectance spectroscopy (UV-DRS), X-ray photoelectron spectroscopy (XPS), specific surface area and pore size analysis (BET), and photoluminescence spectroscopy (PL) were employed to analyze the morphology, structure and elemental composition of Bi_1-xLa_xFe_1-yMn_yO₃ crystals. The results indicate that doping with La and Mn elements can significantly alter the crystal structure and morphology of BiFeO₃, suppressing the recombination of its charge carriers. Using Bi_1-xLa_xFe_1-yMn_yO₃ as a photocatalyst, the effects of pH value and light source on the photocatalytic degradation of simulated pollutants were investigated, and further experiments to explore the photocatalytic mechanism were conducted. The results reveal that La/Mn co-doped samples show significant differences in degradation rates for congo red (CR) and methylene blue (MB), which is related to the electronegativity of the dye molecules. Meanwhile, doping enhances the magnetic properties of the samples, which is beneficial for recycling and improving its utilization efficiency.