The mice spleens isolated from ractopamine-BSA-immunized mice are fused with myeloma cells to generate hybridomas. Hybridoma cells are further injected into the abdominal cavity of mice, producing and obtaining mouse ascites fluid containing ractopamine monoclonal antibody. This monoclonal antibody occurs as an unconjugated IgG1. Its purity is greater than 95% using protein G purified. The target ractopamine is a phenol-based TAAR1 agonist and β adrenoreceptor agonist that stimulates β1 and β2 adrenergic receptors. And this anti-ractopamine monoclonal antibody is suitable for the ELISA assay.