Herein, a strategy was put forward for sensitive label-free electrochemical immunosensor by using silver-graphene oxide (Ag-GO) as redox probe. Initially, a simple, soft reaction conditions and efficient route was designed to in situ reduce silver nanoparticles (AgNPs) onto graphene oxide (GO) by glucose as reducing agent. The obtained nanocomposite gave a pair of well-defined redox peaks with the advantages of good biocompatibility and chemical stability. Furthermore, the GO provided large surface area for assembly of abundant AgNPs with redox activity, which potentially paved sensitive way for immunodetection. Thus, the Ag-GO nanocomposites were used as redox probe to fabricate a sensitive label-free immunosensor for alpha-1-fetoprotein (AFP). In addition, gold nanoparticles (AuNPs) for immobilization of antibody (anti-AFP) could amplify the electrochemical signal and further enhance the sensitivity of the immunosensor due to its excellent conductivity and large surface area. Under the optimal condition, the anodic peak current linearly responded to the logarithm of AFP concentration in a wide range from 0.01 to 100 ng mL(-1) with a low limit of detection of 3 pg mL(-1) (S/N = 3). The designed immunosensor displayed the advantages of simple preparation, high sensitivity, good selectivity and satisfactory stability. (C) 2012 Elsevier Ltd. All rights reserved.