A sensitive label-free amperometric immunosensor was developed based on the amine-functionalized graphene (GR-NH2) and gold nanoparticles (AuNPs) composite modified carbon ionic liquid electrode (CILE). CILE was fabricated by using an ionic liquid of 1-octyl-3-methylimidazolium hexafluorophosphate as binder. The nanocomposite AuNPs/GR-NH2 had prominent biocompatibility, good electron transfer ability, large specific surface area, and primarily excellent adsorption. The negatively charged AuNPs could be adsorbed on the positively charged GR-NH2 modified CILE surface by electrostatic adsorption, and then to immobilize alpha-fetoprotein antibody (anti-AFP) for the assay of alpha-fetoprotein (AFP). The fabricated procedures and electrochemical behaviors of the immunosensor were characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The anti-AFP/AuNPs/GR-NH2 modified CILE was sensitive to AFP in linear relation between 1 and 250 ng mL(-1) with the correlation coefficient of 0.995, and the detection limit (S/N = 3) was 0.1 ng mL(-1) under the optimal conditions. In addition, the proposed immunosensor exhibited good sensitivity, selectivity, stability and long-term maintenance of bioactivity and it may be used to immobilize other biomoleculars to develop biosensor for the detection of other antigens or biocompounds. (C) 2011 Elsevier B.V. All rights reserved.