The invention provides an olefin oxychlorination catalyst and a preparation method thereof. The catalyst comprises a catalyst carrier, alkali metal ingredients, alkaline earth ingredients and rare earth ingredients, wherein the alkali metal ingredients, the alkaline earth ingredients and the rare earth ingredients are loaded on the catalyst carrier, the catalyst carrier comprises copper ingredients and aluminum oxide. The invention also provides a preparation method of dichloroethane, which comprises the following step that under the oxychlorination reaction condition, ethylene, hydrogen chloride and oxygen gas take reaction under the existence of oxychlorination catalysts, wherein the oxychlorination catalysts are the catalysts provided by the invention. When the olefin oxychlorination catalyst provided by the invention is used for preparing the dichloroethane, higher oxychlorination conversion rate and higher dichloroethane yield can be obtained.