Phosphine-catalysed polyaddition of bifunctional ynones with diols or with dithiols is described. By the tri-n-butylphosphine-catalysed polyaddition of aromatic bis(ynone) having benzene ring as a spacer (without methylene group adjacent to carbonyl groups) or aliphatic bis(ynone) having octamethylene group as a spacer with p-xylene glycol, polymers having beta-alkoxyenone moieties in the main chain were obtained in high yield. The polyaddition of the aromatic bis(ynone) gave a polymer composed of specifically E-unit, while that of the aliphatic bis(ynone)s produced a polymer containing both E- and Z-units. Further, the polyaddition with dithiols with bifunctional ynones was also carried out under similar conditions to yield the corresponding polymer composed of both E- and Z-units in almost quantitative yield.