Based on MEMS technology,immunosensor with an“Au,Pt,Pt”three-microelectrode system enclosed in a SU-8 micro pool was fabricated.Employing SAMs technique,the Au electrode was modified by cysteamine(Cys)to assemble gold nanopanicles(nanogold)layer,subsequently,a layer of protein G(PG)was immobilized on nanogold layer to further capture antibody orientedly.Compared with the immunosensors using bulky gold electrode and direct PG binding to electrode immobilization technique for antibody,it has attractive advantages,such as miniaturization,good compatibility,broad linear range for human immunoglobulin(HIgG)and easy to be designed into array. Based on MEMS technology, immunosensor with an “Au, Pt, Pt ” three-microelectrode system enclosed in a SU-8 micro pool was fabricated. Employing SAMs technique, the Au electrode was modified by cysteamine (Cys) to assemble gold nanopanicles (nanogold) layer, subsequently, a layer of protein G (PG) was immobilized on nanogold layer to further capture antibody orientedly. Compared with the immunosensors using bulky gold electrode and direct PG binding to electrode immobilization technique for antibody, it has attractive advantages, such as miniaturization, good compatibility, broad linear range for human immunoglobulin (HIgG) and easy to be designed into array.