A polyacetylene film having a high electroconductivity is prepared by (a) heating a Ziegler-Natta catalyst at a temperature not lower than 150.degree. C. in an organic solvent and then, cooling the catalyst-solvent mixture, (b) removing coarse catalyst particles having a diameter of larger than 1 .mu.m from the catalyst-solvent mixture by filtration to form a catalyst dispersion for polymerization, (c) introducing acetylene into the catalyst dispersion to effect polymerization of acetylene, and (d) drawing the formed polymer and treating the drawn polymer with a dopant.