This invention belongs to the field of fluorochemical technology, specifically relating to a method for preparing cis-1,1,1,4,4,4-hexafluoro-2-
butene. The method includes the following steps: I. Reacting 3,3,3-trifluoropropylene with
carbon tetrachloride under
light irradiation, optionally in the presence of a first catalyst, to obtain 1,1,1,3-tetrachloro-4,4,4-trifluorobutane; II. Reacting the obtained 1,1,1,3-tetrachloro-4,4,4-trifluorobutane with
hydrogen fluoride in the presence of a second catalyst to obtain cis-1,1,1,4,4,4-hexafluoro-2-
butene. The first step of this method uses a light-driven
addition reaction, and the photocatalytic approach significantly reduces production costs. It can also be combined with a dedicated catalyst to improve reaction efficiency. The second step, the fluorination reaction, is adapted to a specific catalyst, which can effectively improve the conversion rate of the reactants and the selectivity of the target product, ensuring the overall high efficiency of the preparation process.