In this paper, the electrochemiluminescence (ECL) detection of a tumor marker by using gold-silver nanocomposite-functionalized graphene as a sensing platform, which increased the surface area to capture a large number of primary antibodies as well as improving the electronic transmission rate. The graphene quantum dots (GQDs) were high quantum yield and high biocompatible which obtained by one-pot simple synthetic strategy. With property of good conductivity and large surface area, porous PtPd nanochains can conjugate more GQDs and second antibody to improve the sensitivity of the immunoassay. As a proof-of-concept, carbohydrate antigen 199 was used as a model analyte. Under optimal conditions, the ECL immunosensors exhibited a wide detection range (0.002-70 U.mL(-1)) and a low detection limit (0.96 mU.mL(-1)). Such immunosensor showed good precision, acceptable stability and reproducibility. In addition, the proposed method provided a new promising platform of clinical immunoassay for other biomolecules. (C) 2014 Elsevier Ltd. All rights reserved.