A process for the preparation of epoxide through a halohydrin process comprises: (1) halohydration: H2O2 (or hydrogen peroxide), halogen elementary substance, ethylenically unsaturated compound having one or more C=C double bonds are added into a reaction apparatus and subjected to halohydration reaction to obtain halohydrin; (2) saponification: the halohydrin of step (1) is subjected to a saponification reaction with an alkali metal hydroxide and the mixture is separated to obtain an epoxide and a halogenated alkali metal salt. The method further comprises: (3) electrodialysis: the halogenated alkali metal salt obtained in the step (2) is subjected to bipolar membrane electrodialysis to obtain an alkali metal hydroxide and a hydrogen halide. In the process of the present invention, the halohydrin or the epoxide is prepared with extremely high selectivity and yield, and the waste water and waste residue are greatly reduced.