Polyether triol with molecular weight distribution index being 1.3～1.5 was prepared in yield around 50% by tetrahydrofuran polymerization using heteropolyacid-H3PW12O40 and ethylene oxide as initiator system and 1

1

1-trihydroxymethylenepropane(TMP) as molecular weight controller.The average hydroxyl functionality was estimated by end-group analysis and VPO to be close or equal to 3. The 1H NMR spectra showed that about 1/3 hydroxyl of TMP did not react with the propagating chains in the THF polymerization.Each of the unreacted hydroxyl groups of TMP attached to the middle or to the end of a diol chain as a pendent primary hydroxyl proup forming the obtained polyether triol.All the hydroxyl of polyether triol were verifid to be active enough towards 4

4'-methylene bis (phenyl isocynate) in the preparation of polyurethanes.