Abstract: A colloidal gold immunoassay methodology was developed using the conjugate of the lab-made monoclonal antibody of diarrhetic shellfish poison,microcystin-LR(MC-LR),and KLH as the labeled substrate.The conjugate was produced following the immune competition law.Colloidal gold with various particle sizes were prepared.The particle size of 30 nm was selected for labeling the antibody.The rapid detection was carried out on an immunochromatographic strip made of a nitrocellulose membrane coated with the conjugate as the inspection band and the goat anti-mouse IgG as the quality control band. Without a need for additional equipment,this newly developed test strip could give a rapid,visual result in 3-5minutes with a sensitivity and a low threshold MC-LR content of 2ng·mL-1.