A method of preparing fluoroelastomer capable of being vulcanized by using peroxide, comprising in the presence of an initiator and a chain transfer agent, conducting emulsion polymerization reaction on comonomers to obtain the fluoroelastomer, characterized in that, the chain transfer agent is alkyl iodide RI x, wherein R is C1-6 alkyl, and x is a natural number ranged from 1-3; wherein the method comprises the following steps adding an emulsifier, a pH regulator and water into a reactor, to obtain an emulsion with emulsifier mass-volume concentration of 0.5-1.0 g/L and pH regulator mass-volume concentration of 0.5-1.0 g/L; wherein - the emulsifier is a mixture composed of perfluoropolyether peroxide and octyl sulfonate at any ratio; and - the pH regulator is selected from dipotassium hydrogen phosphate, disodium hydrogen phosphate, borax or sodium bicarbonate; adding a comonomer into the reactor of step, to allow the pressure of the reactor to reach 0.3-5.0 MPa; wherein the comonomer comprises a first comonomer and a second comonomer; wherein the first comonomer is vinylidene fluoride, and the second comonomer is one or more of hexafluoropropylene, tetrafluoroethylene and chlorotrifluor ethylene; and the molar ratio of the first comonomer to the second comonomer is 30-60:70-40; under a pressure of 0.3-5.0 MPa and at a temperature of 50-120 °C adding an initiator into the reactor to initiate polymerization reaction, and then adding a chain transfer agent thereinto; adding the mixed monomers in portions into the reactor of step, and maintaining the pressure constant in the reactor; and adding the initiator in portions until the polymerization reaction is finished; wherein the molar ratio of the first comonomer to the second comonomer is 60-80:40-20; after the reaction is finished, condensing and washing the resulted polymer to obtain the fluoroelastomer. adding an emulsifier, a pH regulator and water into a reactor, to obtain an emulsion with emulsifier mass-volume concentration of 0.5-1.0 g/L and pH regulator mass-volume concentration of 0.5-1.0 g/L; wherein - the emulsifier is a mixture composed of perfluoropolyether peroxide and octyl sulfonate at any ratio; and - the pH regulator is selected from dipotassium hydrogen phosphate, disodium hydrogen phosphate, borax or sodium bicarbonate; - the emulsifier is a mixture composed of perfluoropolyether peroxide and octyl sulfonate at any ratio; and - the pH regulator is selected from dipotassium hydrogen phosphate, disodium hydrogen phosphate, borax or sodium bicarbonate; adding a comonomer into the reactor of step, to allow the pressure of the reactor to reach 0.3-5.0 MPa; wherein the comonomer comprises a first comonomer and a second comonomer; wherein the first comonomer is vinylidene fluoride, and the second comonomer is one or more of hexafluoropropylene, tetrafluoroethylene and chlorotrifluor ethylene; and the molar ratio of the first comonomer to the second comonomer is 30-60:70-40; the comonomer comprises a first comonomer and a second comonomer; wherein the first comonomer is vinylidene fluoride, and the second comonomer is one or more of hexafluoropropylene, tetrafluoroethylene and chlorotrifluor ethylene; and the molar ratio of the first comonomer to the second comonomer is 30-60:70-40; under a pressure of 0.3-5.0 MPa and at a temperature of 50-120 °C adding an initiator into the reactor to initiate polymerization reaction, and then adding a chain transfer agent thereinto; adding the mixed monomers in portions into the reactor of step, and maintaining the pressure constant in the reactor; and adding the initiator in portions until the polymerization reaction is finished; wherein the molar ratio of the first comonomer to the second comonomer is 60-80:40-20; after the reaction is finished, condensing and washing the resulted polymer to obtain the fluoroelastomer.