A novel electrochemiluminescence (ECL) immunosensor was fabricated by using titanium dioxide (TiO2) and antimony tin oxide (ATO) nanocomposite as electrode modified material to detect aflatoxin B-1 (AFB(1)). Luminol with ECL characteristics was modified on the surface of a platinum electrode to prepare the luminescent electrode. The buffer solution contained hydrogen peroxide (H2O2) was used to monitor the ECL signals owing to the chemiluminescence properties of luminol-H2O2 in alkaline solution. TiO2 and ATO were doped with chitosan to form TiO2@ATO nanocomposite, which was modified on the electrode to enhance the ECL intensity by accelerating the electron transfer and provided more binding sites for aflatoxin B-1 antibody (Ab) and AFB(1). An ECL immunosensor was prepared for AFB(1) detection by modifying Ab and bovine serum albumin (BSA) successively. The specific combination of AFB(1) and Ab weakened the ECL intensity, thus the concentration of AFB(1) was determined according to the strength change of ECL signal. Under optimum conditions, the constructed immunosensor provided a wide linear range from 1.0 x 10(-2) to 1.0 x 10(3) ng mL(-1) with a detection limit of 0.03 ng mL(-1) (S/N = 3) and showed great specificity and high stability. Furthermore, the proposed immunosensor successfully demonstrated its applicability for detecting AFB(1) in peanut oil samples. (C) 2019 The Electrochemical Society.