The invention discloses an immune colloidal gold strip for detecting residue of roxarsone and a preparation method thereof, and belongs to the technical field of immunochemistry quick test for residue of a veterinary drug. The strip comprises a sample pad, a combined pad, a nitrocellulose membrane, a water absorption pad and a PVC back lining; and the immune colloidal gold strip is characterized in that: the PVC back lining is adhered with the sample pad, the combined pad, the nitrocellulose membrane and the water absorption pad in sequence; the combined pad is coated with an anti-roxarsone monoclonal antibody-colloidal gold marker; and the monoclonal antibody is obtained by excretion of a hybridoma cell line. The nitrocellulose membrane is coated with a detection line consisting of a roxarsone-carrier protein conjugate and a quality control line consisting of rabbit anti-mouse IgG. The strip of the invention has remarkable advantages of high sensitivity, strong specificity, simple and convenient operation, rapid detection, accuracy and the like.