Objective To establish an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) for the detection of sulfadimethoxine (SDM) in animal-derived foods.Methods An artificial antigen is synthesized by conjugating SDM with carrier proteins by the diazotization method. A highly sensitive antibody against SDM is prepared by immunizing animals. Based on this, an ic-ELISA is established and the detection system is optimized. Its detection performance is characterized, and spiked recovery tests are carried out.Results When the concentration of the coating antigen is 0.500 μg/mL, the dilution ratio of the horseradish peroxidase-labeled goat anti-rabbit secondary antibody is 1:5000, the reaction time of the primary antibody is 15 min, the reaction time of the secondary antibody is 30 min, and the chromogenic reaction time is 10 min, the established ic-ELISA exhibits an IC₅₀ of 9.33 ng/mL, a detection range of 0.76~114.82 ng/mL, and a limit of detection of 0.74 ng/mL, with good precision and specificity, and satisfactory spiked recovery rates in milk, chicken, and pork samples.Conclusion This method can be applied to the sensitive, precise, specific and accurate detection of SDM residues in real samples of milk, chicken, and pork, providing an effective means for efficient on-site screening.