A new strategy to constructing amperometric immunosensor for transferrin assay based on improved carbon paste electrode (CPE) as sensing platform has been described. The CPE is prepared by employing polyvinyl alcohol-doped polystyrene as the novel adhesive. The obtained CPE has good conductivity and better surface -adsorption capability. A sequential competitive immunoassay format was performed on the surface of CPE by using transferrin and transferrin antibody as a model system. The assay comprised first loading of the transferrin antibody on surface of CPE, then blocked in BSA solution followed by a competitive incubation in the buffer containing the transferrin (analyte) and transferrin labeled with horseradish peroxidase (SjAg-HRP) and finally the amperometric detection. The feasibility of regenerating surface of CPE for consecutive assays is demonstrated by a simple polish after each determination. The dynamic concentration range for transferrin assay is 0.50～70.0 μg/mL.