A novel procedure for immobilizing orientation-controlled antibodies was investigated using tyrosinase catalyzed immobilization of Staphylococcal protein A (SpA). We synthesized well-defined structured block-type polymer, poly(2-methacryloyloxyethyl phosphorylcholine(MPC)-block-2-aminoethyl methacrylate (AEMA)) (PMbA) from the substrate by surface-initiated living radical polymerization for bioconjugation. One of the segments in the PMbA, poly(MPC) provides hydrophilicity and biocompatibility and the other segment, poly(AEMA) possesses amino groups for conjugation with biomolecules. On this PMbA polymer grafted substrates, SpA is first oxidized by tyrosinase and then immobilized to the amino group of the substrate through the active quinone groups in the SpA. The PMbA substrates showed a good resistance for non-specific protein adsorption, due to its primal layer of poly(MPC) segments. As the result of sandwich immunoassay, this system using tyrosinase and SpA showed the best primary antibody/secondary antibody ratio among the system without SpA and that with randomly oriented SpA. This procedure can be further utilized for achieving higher sensitivity of immunoassay systems.