Cyclopolymerization of 4,4-bis(pivaloxymethyl)-1,6-heptadiyne containing a bulky ester group was examined by group 5,6-transition metal catalysts. Both of the MoCl5-based and WCl6-based catalysts were effective for the cyclopolymerization. The obtained polymer was characterized to have planar backbone and recurring cyclic ring structure by various spectroscopy. The poly[4,4-bis(pivaloxymethyl)-1,6-heptadiyne] was soluble in common organic solvents to easily cast the free standing film. The polymer film had good mechanical property and high oxygen permselectivity to nitrogen. The oxygen permeability coefficient (PO2) and permselectivity of oxygen to nitrogen (PO2/PN2) of poly[4,4-bis(pivaloxymethyl)-1,6-heptadiyne] were 19.7 barrer and 5.71, respectively.