Using prepolymerized glycidyl azide polymer （GAP） as soft segments,4,4′-diphenylmethane diisocyanate （MDI） and 1,4-butanediol（BDO） as hard segments for the purpose of insensitive high energy propellants,an energetic thermoplastic elastomer(ETPE) was synthesized by melt-prepolymerization,and was characterized by FTIR,TG,tensile strength test and DMA. The results show that the reaction time and aging time for ETPE synthesization are 2 h and 3 d respectively. And the tensile strength (δ) of the ETPE is 6.12 MPa,and the elongation(ε) is 71% when hard segment is 40% in weight and the mole ratio of —NCO to —OH （R） is 0.98. After adding plasticizer BDNPF／A(A3) in the ETPE,δ is invariability,but the elongation decreases.