To develop a more sensitive immunologic method for SM₂ detection. MethodsAn indirect competitive chemiluminescence immunoassay was established with SM₂ monoclonal antibody, and was used to detect the SM₂ residue in animal derived foods. ResultsThe results indicated that the SM₂-mAb belongs to subclass of IgG_2b, and its affinity constant was 0.12×10⁷L/mol. The detection limit of SM₂-CLEIA was 0.174 μg/L with the linear range of 0.1 to 1 000 μg/L (r²=0.990 4), and IC₅₀ was 4.006 μg/L. The recoveries were from 94.41% to 104.40%. The variability within and between batches were 3.07% and 8.22%, respectively. There was no significant cross reaction between SM₂-mAb and SG or other drugs, and the results were 100% in accordance with those of the SM₂-ELISA kit.ConclusionSM₂-CLEIA was established, which was sensitive, specific, precise and with wide linear range.