The invention discloses a preparation method of 3-chloropyridine. 3-chloropyridine is a fine chemical engineering intermediate extensively used in the fields of medicine and pesticides. The preparation method comprises the following steps of: taking 2,6-dichloropyridine as a raw material and performing chlorination reaction to obtain 2,3,6-trichloropyridine; putting the 2,3,6-trichloropyridine, an acid-binding agent, a metal catalyst and an organic solvent into a reactor for performing hydrogenation reaction, wherein the mol ratio of the 2,3,6-trichloropyridine to the acid-binding agent is 1:(0.5-1.0); cooling the hydrogenation reaction liquid, adding water to dissolve the hydrochlorate of the acid-binding agent, filtering and standing to separate the water layer; extracting the organic solvent layer by aqueous acid at least more than three times; combining the extracted aqueous acid layers, thinning up with water, alkalizing for adjusting the pH value of the filtrate to be 7; and layering the filtrate to obtain the liquid product of 3-chloropyridine. The preparation method of 3-chloropyridine has a novel process route, short reaction steps, simplicity of operation, high yield, low production cost and environmental friendliness, and is suitable for industrialized production.