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