A novel electrochemical sensor for the detection of sulfur dioxide in both gas and solution is described. The chemically modified electrode was constructed by polymerizing (4-VP), palladium and iridium oxide (PVP/Pd/IrO(2)) onto a platinum microelectrode which exhibits excellent catalytic activity toward sulfite with an oxidation potential of +0.50 V. The SO(2) gas sensor is based on the PVP/Pd/IrO(2) modified electrode as working electrode, Ag/AgCl electrode as reference electrode, Pt electrode as counter electrode and a porous film, which is in direct contact with the gas-containing atmosphere. The effect of different internal electrolyte solutions of hydrochloric acid, sulfuric acid, phosphates buffer solution, mixed solution of dimethyl sulfoxide and sulfuric acid to the determination of SO(2) was also studied. The sensor was found to have a high current sensitivity, a short response time and a good reproducibility for the detection of SO(2). It has good potential to be used in the field of environmental monitoring and controlling.