Abstract: Polyclonal antibodies (PcAbs) and monoclonal antibodies (McAbs) against sulfamethazine (SM₂) were obtained. The association constants (K_a) of the antibodies are all higher than 10⁸ L/mol. The enzymelinked immunosorbent assay (ELISA) for the measurement of SM₂ was set up by using PcAb2510. The assay range for this method is 0.1-30 ng/mL and the sensitivity is 0.08 ng/mL. The intraassay and interassay coefficients of variation (CV) vary from 12.8%-14.1% and 14.0%-20.5%, respectively. The recovery of the analyte in different samples is from 80.5% to 137.8% and the experimental correlation coefficient of dilution is found to be 0.997.