The invention relates to the technical field of organic synthesis and concretely relates to a preparation method of chloroethyl-n-propylether. 2-n-propoxyethanol and thionyl chloride as main raw materials undergo a reaction in the presence of a high-efficiency nucleophilic catalyst, wherein through dropwise addition of thionyl chloride, a reaction rate is strictly controlled, the product is heated and is subjected to thermal insulation to form a crude product, and the crude product is subjected to rectification purification to form chloroethyl-n-propylether. The product has clear and transparent appearance, purity of 99.2% or more, a yield of 98.5% or more and water content of 0.2% or less. Compared with the traditional technology, the preparation method does not produce waste water, realizes recycle of a front cut fraction and kettle bed material produced by rectification and a catalyst, realizes high purity, high yield and low water content and is suitable for industrial production.