A synthesis of an energetic prepolymer used as a high-energy binder for an insensitive and high performance explosive is disclosed. More specifically, provided are a novel compound 2-nitratoethyl oxirane expressed by formula III, a novel compound poly(2-nitratoethyl oxirane) expressed by formula IV, obtained by polymerization of 2-nitratoethyl oxirane used as a monomer and a preparation method thereof. The compound, used as an energetic prepolymer and a monomer for preparation thereof can substitute for existing poly(glycidyl nitrate) (PGN) which has been known to be a promising one having the best performance among existing energetic prepolymers, but which has a problem to be self-decomposed after synthesis of polyurethane elastomer, to solve this problem.