In this work, a sensitive sandwich-type electrochemical immunosensor was designed for detecting carcinoembryonic antigen (CEA). The porous PtCu nanocrystals loaded on amino-functionalized copper sulfide nanospheres (P-PtCu/FCuS NPs) were used as labels to amplify detection signals. The P-PtCu/FCuS NPs with abundant active sites, large surface area and good biocompatibility, which could efficiently enhance the catalytic performance of the immunosensor as well as increase the number of immobilize secondary antibodies. The gold nanoparticles loaded on sulfonated multi-walled carbon nanotubes (Au/s-MWCNTs) were used as platform, which not only provided large specific surface area to increase the loading of primary antibodies, but also accelerated electron transfer on the surface of electrode. Under the optimal conditions, the immunosensor obtained a good linear ranging between 10 fg mL(-1) and 10 ng mL(-1), and with the detection limit of 3.3 fg mL(-1) (S/N = 3). Meanwhile, the proposed sandwich-type immunosensor exhibited satisfactory performance in detecting serum samples, indicating the great potential in clinical analysis applications. (C) 2019 The Electrochemical Society.