Abstract: In older to increase the miscibility of ethylene oxide-tetrahydrofuran copolymers with nitiates (NG, BTTN and NG+BTTN), the preparation condihons for higher ethylene oxide ratios and higher molecular weight products were studied. A bulk polymerization can be only use for preparing higher ethylene oxide content copolymers with moledar weight less than 4000 by increasing the tempelature in latter reaction period and adding catalysts again and prolonging reaction time, etc. The products of the molecular Weight higher than 4000 can be prepared in solvent polymerization by prolonging reaction time. The acidic catalyst in raw copolyether can be diminished with active alumina.