The invention provides a preparation method of 2,3-dichloro-5-trifluoromethylpyridine. The preparation method comprises the following steps: (a) 2-chloro-5-chloromethyl pyridine is provided; (b) in the presence of a catalyst, 2-chloro-5-chloromethyl pyridine from the step (a) and a chloride agent chlorine undergo a chlorination reaction so as to obtain 2,3-dichloro-5-trichloromethylpyridine, wherein the catalyst is oxide of copper, chloride of copper or a combination of the oxide of copper and the chloride of copper; (c) after heated and dissolved, 2,3-dichloro-5-trichloromethylpyridine obtained from the step (b) undergoes a fluoridation reaction with hydrogen fluoride under the action of a catalyst so as to obtain 2,3-dichloro-5-trifluoromethylpyridine, wherein the catalyst is oxide of antimony or halide of antimony. By the above method, production cost is reduced, conversion rate is raised, and toxicity is decreased.