Abstract1‐Ethynylcyclohexene, an acetylene derivative having cyclohexenyl substituent, was polymerized by various W‐ and Mo‐based catalysts. WCl6‐EtAlCl2catalyst system was found to be very effective for this polymerization. The effects of the monomer‐to‐catalyst mol ratio, the initial monomer concentration, the temperature, and the cocatalysts for the polymerization of 1‐ethynylcyclohexene by WCl6were investigated. The catalytic activity of Mo‐based catalysts was found to be similar to that of W‐based catalysts. The polymer structure was identified to have a conjugated polymer backbone carrying a cyclohexenyl substituent. The resulting polymers were light‐brown powder and completely soluble in aromatic and halogenated hydrocarbon solvents such as chlorobenzene, benzene, chloroform, carbon tetrachloride, etc. Studies of the thermal properties and morphology of poly(1‐ethynylcyclohexene) were also carried out. © 199