Abstract: Developing a rapid and easy-handled test strip based on colloidal gold immunochromatographic assay，for detecting Clenbuterol residue in pig urine.The strip was successfully developed by adopting the immunochromatographic competition method. If the content of Clenbuterol residue in the sample is below a threshold quantity，most of the nanocolloidal gold-labeled anti-Clenbuterol monoclonal antibodies （Anti-CLB Mabs） bind to the solid support，forming a visible red blot. If the content of Clenbuterol residue in the pig urine is beyond the threshold quantity，Clenbuterol residue in the sample would compete with CLB-BSA for binding to the limited amount of gold-labeled Anti-CLB Mabs，they would bind to the anti-CLB Mabs in the first place，so that reducing the probability of forming Anti-CLB Mab and CLB-BSA combination，as a consequent，no visible red blot would be seen. A highly sensitive rapid colloidal gold test strip which could detect down to 2 ng/mL was successfully developed and produced; test could be done and visualized within 8 min. The sensitivity of this product has achieved the requirement for clinical use. Test could be done without any scientific instruments. The product is highly sensitive，specific，rapid，and easy-handled for rapid test，especially for on-site screening.

Key words: clenbuterol; strip; colloidal gold; immunoassay; rapid test