A novel chemically modified electrode based on the immobilization of heteropolytungstate in carbon nanotubes-chitosan (CNTs-chitosan) composite film by one step self-assembly technique was fabricated. Chitosan was chosen as a natural polymer for dispersing CNTs to form a stable CNTs-chitosan composite, which provided an interface containing amino groups for assembling [P2W18O62](6-) (abbr. P2W18) by electrostatic interactions. The CNTs-chitosan composite film was investigated and characterized by infrared spectroscopy (IR), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The CNT-chitosan film provides a high active area and good conduction pathway, and enhances the adsorptive capability of P2W18 molecules on the film. The electrochemical behavior of the P2W18/CNTs-chitosan/GCE was studied in detail, including scan rate, pH dependence, and stability. The CV and amperometry studies demonstrate that the P2W18/CNTs-chitosan/CCE has fast response and good electrocatalytic activity for the reduction of S2O82- and IO3- anions in acidic aqueous solution. (C) 2009 Elsevier Ltd. All rights reserved.