Using water and toluene as solvents,and quaternary ammonium salt as phase transfer catalyst,under the effect of NaOH,3,3-dibromomethyl oxetane (BBMO) was synthesized by the cylization of 1,1,1-tribromomethyl-1-hydroxymethyl methane. Using water as solvent,quaternary ammonium salt as phase transfer catalyst,3,3-diazido methyloxetane (BAMO) was obtained by the substitutation of BBMO with NaN₃. The prepolymer of BAMO (PBAMO) was synthesized by the cationic polymerization of the monomer BAMO,and it had a number average molecular weight from 3000 to 4000. The chain-extended PBAMO (CE-PBAMO) was synthesized by the chain extended of the PBAMO with 2,4-toluene diisocyanate (2,4-TDI) and 1,4-butanediol (1,4-BDO). The structure and physical chemical properties of BBMO,BAMO,PBAMO and CE-PBAMO were identified by FTIR,¹H NMR,HPLC,DSC and GPC. The results show that the yield and purity of BBMO are 81% and 97.2%,and the yield and purity of BAMO are 80.9% and 98.37%; the synthesis of BBMO and BAMO by phase transfer catalysis possesses advantages of safety,high yield and high purity; the synthesized CE-PBAMO which has a number average molecular weight of 38933,can melt and dissolve,and its tensile strength is 12.7 MPa at 20 ℃,it can be used as high energy thermoplastic binder in the manufacture of the new type of combustible cartridge case which has concept of 3R(recycle,recover,reuse).