The invention discloses a preparation method of epoxybutane. The preparation method comprises the following steps: performing reactive distillation on an ethanediol and 1,2-butanediol-containing raw material and an esterifying agent under the action of an esterifying catalyst to respectively obtain a light component containing a reaction product corresponding to the esterifying agent and a heavy component containing ethylene carbonate and butylene carbonate, rectifying the heavy component containing the ethylene carbonate and the butylene carbonate to respectively obtain the ethylene carbonateand the butylene carbonate, and decarboxylating the butylene carbonate under the action of a decarboxylating catalyst to obtain the epoxybutane. According to the preparation method of the epoxybutane, the ethanediol and 1,2-butanediol-containing raw material and the esterifying agent are subjected to ester exchange reaction, so that 1,2-butanediol is converted into the butylene carbonate which isnot azeotropic with ethanediol to purify the ethanediol, and the butylene carbonate obtained by the conversion of the 1,2-butanediol is decarboxylated to obtain the epoxybutane with a relatively highadditional value.