Epoxy resin E51 was toughened and modified using epoxy-terminated polybutadiene liquid rubber (ETPB). As a reactive toughening agent, it is found that ETPB is suitable for medium-to-normal curing temperature and can be mixed with epoxy resin at a high addition ratio of 1000% and achieve simultaneous curing. ETPB can enhance the interaction between rubber dispersed phase and epoxy resin, and promote the formation of the two-phase structure, which intensifies the toughening effect. By introducing novel polyether amine curing system, a semi-transparent epoxy composite material with high elongation at break was obtained. ETPB/E51 blends with a wide mass ratio of 1 ∶ 10 to 10 ∶ 5, can achieve tensile strength of 1.57 MPa to 11.86 MPa and elongation at break of 31% to 262% by adjusting curing system, which show excellent tensile properties. An elastic epoxy system at wide temperature range ( -45 ℃ to 70 ℃) with low addition of ETPB was reported by synergistic toughening of inorganic nanoparticles, which is expected to be applied under extreme conditions such as deep space and deep sea.