Salicylic acid (SA) is one of essential phytohormones in the regulation of many physiological processes, especially for the defense of plants under various biotic stresses. Although SA could be electrochemically detected with various ways, their application was limited by unsatisfactory detection performance, or the requirement of acid/alkaline solutions. In this study, glassy carbon electrodes (GCEs) were coated with chitosan (CS) and then modified using the nanocomposite of Au@Fe3O4 for the detection of SA. It was found that the Au@Fe3O4-CS modified GCEs could be applied for the electrochemical determination of SA in the Britton-Robinson buffer solution at pH 7.0. After the optimization of the concentration of Au@Fe3O4 and the pH value of the buffer solution for detection, the concentration of SA could be measured with the linear range from 1.0 mu M to 1.2 mM and the lowest detection limit at 0.10 mu M based on differential pulse voltammetry. The electrochemical response of SA at the Au@Fe3O4 modified GCEs was stable and reproducible. Moreover, the modified electrodes were applied for monitoring time-dependent variation of SA extracted from normal leaves of tomatoes and those infected by fungal pathogen. Our investigation revealed that the Au@Fe3O4 modified GCE could effectively determinate SA in mild conditions with a wide linear range, which can be potentially applied for the study of defense mechanisms of plants. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.