Cationic ring-opening polymerization behavior of six-membered cyclic sulfite (1) was examined. 1 was prepared by the reaction of 1,3-propanediol with SOCl2 in 80% yield. Cationic ring-opening polymerization of 1 was carried out in the presence of cationic initiators such as benzyl bromide (BnBr), BF3 . OEt(2), trifluoromethanesulfonic acid (TfOH), and methyl trifluoromethanesulfonate (TfOMe) in bulk to afford a polymer consisting of sulfite and ether moieties. The content of the poly(ether) unit was estimated to be 30-90%. The relative rate of polymerization by the initiators was estimated to be TfOH:TfOMe:BF3 . OEt(2) = 3.5:2.5:1.0. Judging from the time-conversion curves and time-poly(ether) production curves, the elimination of sulfur dioxide in the propagating end of the polymer was confirmed to depend on the character of the counteranion.