The copolymerization of epoxy-terminated poly (ethylene glycol methyl ether) (CH3PEG-epoxide) with low molecular weight epoxides such as phenyl glycidyl ether (PGE) was carried out to prepare the PEG graft polyethers. Potassium tert-butoxide was the most favorable catalyst used to obtain the graft polyethers. The apparent number-average molecular weight (M(n)BAR) of the graft polyethers decreased with increase in PGE concentration because PGE acted as both solvent and comonomer. The composition of the graft polyethers (PGE/CH3PEG), however, increased with increase in PGE concentration and was almost consistent with the feed ratio of the two monomers. The graft polyethers whose composition was over 10 were insoluble in water. The M(n)BAR of the graft polyethers was little affected by the reaction temperature, but more affected by the presence of solvent. Besides PGE, n-butyl glycidyl ether and styrene oxide were effective as comonomers. CH3PEG-epoxide hardly polymerized in tert-butyl alcohol.