The invention discloses a method for preparing perfluoro-2,3-epoxy-2-methylpentane. The method comprises the following steps: a) providing a mixed solution of perfluoro-2-methyl-2-pentene, an oxidation catalyst and a reaction medium; b) controlling the reaction temperature and the pressure, inflating oxygen, and synthesizing by a molecular oxygen oxidation method to obtain the perfluoro-2,3-epoxy-2-methylpentane. By the method, the reaction yield is high; the reaction medium can be repeated for many times, so that the waste liquid production is greatly reduced; the way is environmentally friendly.