The invention relates to a method for preparing hexafluoro-1,3-butadiene. The method comprises the following steps: performing reduction dechloridation on 1,2-dichloro-1,1,-2-halothane with zinc powder to obtain a CF2=CHF gas phase intermediate product, introducing into liquid bromine to carry out an addition reaction, and obtaining CBrF2CHBrF; evaporating CBrF2CHBrF in an evaporator to generate a gas, and using a reaction tube filled with a first catalyst to remove one molecule HBr and generate trifluorovinyl bromide; performing two steps of reactions on the trifluorovinyl bromide under the action of the zinc powder, the solvent and a second catalyst, thereby obtaining the hexafluoro-1,3-butadiene. The method has the advantages of being simple in process, high in yield, easy in raw material obtaining, easy in industrialization, green and environment-friendly.