One novel hydroxyl-terminated block copolyether(PTHF-PEO-PTHF)was synthesized by tetrahydrofuran cationic ring-opening polymerization and linkage of polytetrahydrofuran with two terminals of polyethylene glycol (PEG),using PEG as macroinitiator,boron-trifuoride ethylether complex (BF₃·OEt₂) as catalyst,and epoxy propane(PO)as assistant ring-opening . The obtained copolyether was characterized by IR and ¹H NMR. Moreover,polyurethane elastomers were prepared with hydroxy terminated polyether （HTPE）,and the elastomers have satisfactory mechanical properties,low glass transition temperature(T_g=-69.03 ℃),and good thermal stability. These can meet the requirements of binder for solid propellant.