3 bis(azidomethyl)oxetane(BAMO) and tetrahydrofuran (THF) were synthesized by cationic ring opening copolymerization and its molecular structure was characterized by IR and 1H-NMR. The chain structure of the polyethers was analyzed with 13C-NMR. It has been found that the feed ratio is good to equalize the chain segmental ratio fairly.