A micro amperometric immunosensor is fabricated to detect human IgG based on MEMS. The Pt electrode is deposited on silicon wafer with the sensitive area of 1 mm2. A micro reacting pool is made of SU-8 polymer and several microlitre reagent was needed. Polypyrrole is electropolymerized on the electrode to transfer the electron between the electrode and the enzyme. Glutaraldehyde is used to bind the antibody on polypyrrole. Human IgG is specifically recognized by goat anti-human IgG and horseradish peroxidas...