Disclosed herein is a method of preparing a perfluoroalkadiene. A dihaloperfluorocarbon used as a starting material is added dropwise to a nonpolar organic solvent, a metal powder and an organic metal compound. The dihaloperfluorocarbon is slowly added dropwise in a temperature range from 30° C. to 150° C. for a certain period of time. Moreover, the nonpolar organic solvent used may be benzene, toluene, xylene, etc., and the organic metal compound is used by being dissolved in ethyl ether or tetrahydrofuran at a concentration of 1 to 3M. The metal powder used may be Mg, Zn, Cd, etc.