In this paper, a novel Ag NPs-PANI/MnO2 tag was synthesized for the first time, and the electrochemical immunoassay for carcinoembryonic antigen (CEA) was achieved. In this experiment, gold nanoparticles (Au NPs) were used as an electrochemical sensing platform to increase conductivity and improve electrode surface capture antibody (Ab(1)). We use PANI as a green sacrificial agent reduces Ag NPs and MnO2, while improving the conductivity and electrochemical stability of the immunosensor. MnO2 and Ag NPs effectively raise the sensitivity of the sensor by catalytically reducing hydrogen peroxide (H2O2) into water and oxygen to achieve a double amplified sensing signal. It is found that the surface plasmon resonance of Ag NPs has an interesting SERS characteristic structure, and the equivalent circuit simulation of the electrode assembly process results in an error of less than 10%, indicating that the electrochemical immunosensor is successfully prepared. Under optimal conditions, the electrochemical immunosensor has a linear range of 0.0005 -80 ng/mL and a detection limit of 0.17 pg/mL (S/N = 3). The immunosensor is expected to be used in clinical laboratories to detect CEA and other tumor markers in human plasma for precancerous screening or surveillance. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.