To establish a rapid method for the determination of metalaxyl residues in aquatic products, in this paper, the metalaxyl colloidal gold immunochromatographic test strip was based on the immunological method of monoclonal antibody, the colloidal gold labeled metalaxyl, monoclonal antibody was used as gold pad, and metalaxyl-bovine serum albumin conjugate and goat anti-mouse IgG as detection line and quality control line. The results showed that the monoclonal antibody of metalaxyl was IgG1, Kappa type; heavy chain 50 ku, light chain 20 ku, molecular mass about 150 ku; affinity constant was 2.46×10⁹ L/mol; IC₅₀ was 59.57 ng/mL. The test strip can still detect when the mass concentration of metalaxyl is 5 mg/mL, and there was no cross-reactivity with enrofloxacin, sulfamethoxazole, florfenicol, furazolidone, praziquantel, doxycycline, malachite green, methylene blue. The test strips were used to test the aquatic products such as Ctenopharyngodon idellus, Ruditapes philippinarum and Penaeus vannamei. The minimum detection limit for Ctenopharyngodon idellus and Penaeus vannamei samples was 2 mg/kg. The minimum detection limit for Ruditapes philippinarum sample was 1 mg/kg. The test strips were verified by high performance liquid chromatography to detect the residues of metalaxyl, and the results were consistent. Conclusion:The monoclonal antibody-based colloidal gold immunological strip is rapid, sensitive and specific, and is suitable as the primary screening method for the detection of metalaxyl residues in aquatic products.