Electrolytic Polymerization of acrylonitrile was conducted under various conditions in the presence of a small amount of hexamethylphosphoramide (HMPA)-Lithium chloride solution, and polymer films were formed on the aluminum cathode plates. The yield of polymer was increased with the increase of the concentration of HMPA-LiCl solution and current density. However, current efficiency and film resistance were decreased with the increasing current density. It was suggested that the coloration during the electrolysis shows the formation of solvated electrons, by which the polymerization of acrylonitrile is provoked.