The invention provides a preparation method of fluororubber capable of being vulcanized by peroxide. The method comprises the following steps: 1) adding deionized water, a pH buffer agent and an emulsifier to a reaction kettle, carrying out vacuum supply operation on the reaction kettle, and heating the inside of the kettle to 50-120 DEG C; 2) adding a polymeric monomer A and a polymeric monomer B to the reaction kettle until the pressure in the kettle reaches 0.3-5MPa, adding a radical initiator to initialize polymerization reaction, adding a chain transfer agent after reaction is begun, simultaneously supplementing the polymeric monomer A and the polymeric monomer B, so as to maintain the pressure at the pressure in the kettle; 3) supplementing the radical initiator once at an interval of 4 hours along with reaction until the reaction is ended; and 4) obtaining an elastomer emulsion, adding a flocculant, condensing, washing and drying in vacuum, so as to obtain the fluororubber capable of being vulcanized by the peroxide. The fluororubber product vulcanized by the peroxide provided by the invention can be vulcanized by the peroxide, so that the permanent compression deformation resistance after hot air ageing is greatly improved.