Alpha-fetoprotein (AFP), mainly synthesized in fetal liver, was a highly specific and heightened sensitive tumor marker for primary liver cancer. The increase of the AFP concentration in adult serum may be an early sign of some cancer diseases. Therefore, it is necessary to detect its concentration in clinical diagnosis to improve diagnostic accuracy and efficiency. Currently, many analytical techniques have been developed as a standard method for the determination of AFP, including Enzyme-linked immunoassay, time-resolved fluoroimmunoassay, surface plasmon resonance, atomic absorption spectroscopy, chemiluminescence fluorescence method, high-performance liquid chromatography (HPLC), and high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS), which are sensitive and accurate. However, these methods typically require well-equipped laboratory facilities, time-consuming sample pretreatment and skilled operators, which significantly limit the applications for fast-screening of large amounts of practical samples. Herein, an ultrasensitive sandwich-type electrochemiluminescence (ECL) biosensor for the analysis of Alpha-fetoprotein (AFP) antigen was fabricated based on CdTe doped silica nanoparticles on graphene oxide (CdTe@SiO₂/GO) nanocomposites as carrier to immobilize labeled AFP antibody and chitosan/multi-walled carbon nanotubes (CS/MWCNTs) composite as carrier to immobilize capture AFP antibody. In this project, capture antibodies were immobilized through covalent combination which could catch the target AFP protein as much as possible. High ECL signal could be obtained due to the luminant CdTe@SiO₂/GO produced larges number of the emission photons. Because of its good conductivity and high surface area, the CS/MWCTs composite material, on the one hand, accelerated the electron transfer rate of electrode surface, on the other hand, it improved the loading rate of capture antibody and labeled antibody, thus further obtaining the high ECL intensity and improving the sensitivity of the sensor. In this strategy, under optimized conditions, the ECL intensity increased with the logarithmic values of AFP standard concentrations from 1.0 pg·mL^-1 to 100 ng·mL^-1 with a detection limit of 0.22 pg·mL^-1 (at an S/N ratio of 3). The ECL immunosensor provided detection method with satisfactory recoveries, excellent reproducibility and stability, indicating that this method had a prospect in the practical application in the clinical diagnosis of AFP.