A series of thermoplastic polyurethane elastomers(TPUEs) with bonding function which can be used as propellant binders were synthesized from polyethylene/polypropylene adipate diol(PEPA), tetrahydrofuran/ethylene oxide copolyether(PET), isophorone diisocyanate(IPDI), 1, 4-butanediol (BDO) and diethyl bis(hydroxymethyl) malonate(DBM) as primary substances by melt pre-polymerization method. Then Fourier transform infrared spectroscopic(FTIR), gel permeation in chromatography(GPC), differential scanning calorimetry(DSC) and tensile test techniques were employed to characterize the structures and properties of TPUEs. Results show that the microphase segregation of TPUEs become more obvious with the BDO content in chain extenders increasing. When the molar content of BDO exceeds 50% in chain extender, the glass transition temperature of soft segment become lower than -70 ℃. It is also observed that tensile strength of the TPUE increased with the BDO content increasing, while the elongation to break decreased. TPUEs extended with mixed diols have better effect than that extended with BDO or DBM to improve the mechnical properties of modified double-based propellant.