A photoelectric material poly(3,4-ethylenedioxythiophene)sulfonate (PEDOT-S) with better watersoluble ability was synthesized by the enzymatic-catalyzed method using sodium 4-(2,3-dihydrothieno [3,4-b] [1,4]clioxin-2-yl)-methoxybutane-l-sulfonate (EDOT-S) as monomer, horseradish peroxidase (HRP) enzyme as catalyst, and hydrogen peroxide (H2O2) as oxidant. This enzymatic catalyzed polymerization is a "green synthesis process" for the synthesis of water-soluble conjugated PEDOT-S, which was carried out with no organic solvent, no water-soluble polyelectrolyte such as polystyrenesulfonate (PSS), no metallic catalyst and no high reaction temperature. UV-Vis spectrum of PEDOT-S changing immediately on varying the pH of the solution showed that the self-acid-doping had occurred. Thermogravimetric (TG) analyses indicated the presence of a stable form of polymer. Atomic force microscopy(AFM) images illustrated that the acid PEDOT-S aqueous solution can form excellent homogeneous and smooth films, while the basic aqueous solution induces the aggregation of polymer. (C) 2018 Elsevier B.V. All rights reserved.