Abstract: People are more and more interested in polythiophene because of its night stability.At present,organic solvent system is still commonly used in electrochemical polymerization of thiophene and the related electrochemical studies.However,it is more practical to use aqueous solutions instead of organic solvents.The electrochemical polymerization of thiophene in aqueous solution of acid is discussed in this paper.In highly concentrated acidic solution,thiophene first undergoes low polymerization,and then the low polymer can be oxidized at the comparatively negative potential to form film.