The invention discloses an energetic material 4, 4, 8, 8-tetranitroadamantane-2, 6-dinitrate and a preparation method thereof. According to the preparation method, cyclooctadiene as the raw material undergoes the steps of hydroboration-oxidation, oxidation, formylation, cyclization, nitric acid esterification, oximation, germinal nitration and the like to be finally synthesized into 4, 4, 8, 8-tetranitroadamantane-2, 6-dinitrate. Polynitroadamantane and adamantine nitrate have the advantages of symmetrical structure, high density, excellent explosion property, low sensitivity and the like, and can be widely used in the fields of explosives, propellants, pyrotechnic compositions, fuels and the like.