The polymerization of tetrahydrofuran ( T H F) initiated by heteropolyacid H3 P W12 O40( P W12) in low concentration could be effectively promoted by propylene oxide( P O) . The polymerization conversion reached 50 % ～60 % after a reaction time around 5 h . Wateror butylene glycol was used to controlthe molecular weightofthe productin the rangeof 1000 ～3000 . The polymerization started upon addition of P Oand stopped with completeconsumption of P O,but it would start again when a new portion of P O was added . Theaverage hydroxyl end group functionality of polyether glycol is close to 2 . The ratio ofprimary and secondary hydroxyl end groups is close to one ,and the percentage of thehydroxyl group attached to P O moietiesatthe polymerchain endsis higherthan 50 % ofthetotal hydroxyl end groups. All the obtained results inferred that T H F polymerizationpromoted by P Oproceeded quite similar to that promoted by ethylene oxide,i.e., P O wasnecessary in theinitiation of T H Fpolymerization to startthe propagation ofchains,and withthe complete consumption of P Othe propagating chains transformed into dormant species,which can be re initiated by the addition ofa supplementary portion of P O. The polymerization of tetrahydrofuran (THF) initiated by heteropolyacid H3 P W12 O40 (P W12) in low concentration could be highly promoted by propylene oxide (PO). The polymerization conversion reached 50% ~ 60% after a reaction time around 5 h. butylene glycol was used to control the molecular weight of the product in the range of 1000 ~ 3000. The polymerization started upon addition of P Oand stopped with completeconsumption of PO, but it would start again when a new portion of PO was added. Theaverage hydroxyl end group functionality of polyether glycol is close to 2. The ratio of primary and secondary hydroxyl end groups is close to one, and the percentage of the hydroxxyl group attached to PO moieties of the polymer chain ends is higherthan 50% of the total hydroxyl end groups. All the obtained results inferred that THF polymerization promoted by P Oproceeded quite similar to that promoted by ethylene oxide, ie, PO wasnecessary in theinitiation of T H Fpolymerization to start the propagation of chains, and with the complete consumption of P Othe propagating chains transformed into dormant species, which can be rewritten by addition of a supplementary part of P O.