A new method has been developed and applied in a micro amperometric immunosensor to immobilize antibody with electropolymerized staphylococcal protein A (SPA). SPA is usually used directly as an immunoadsorbent and can achieve the binding of IgG very well. In this paper, pyrrole doped with SPA was co-electropolymerized onto the working electrode surface by cyclic voltammetry in 10 minutes. It effectively immobilized SPA on the surface of the working electrode for orientation-controlled immobilization of capture antibodies. This method as a controllable and convenient manipulation can modify the sensing surface more rapidly with less consumption of reagent (10μL), which is proper to the micro immunosensor. As an application to test the validity of this method, Salmonella typhimurium (S. typhimurium) with the concentration of 102cfu/ml could be detected by this immunosensor, which shows the good property of the sensor and proves the feasibility of the method applied for the immobilization of antibody. It is potential to develop a biosensor that can be used for convenient, low-cost and real-time sensing of pathogens in food products.