The invention discloses a preparation method of 2-amino-5-chloropyridine, and belongs to the technical field of medicine intermediate synthesis. According to the preparation method, 2-aminopyridine istaken as a raw material, a saturated sodium chlorate aqueous solution is taken as a reaction solvent, TEBA is taken as a catalyst, Cl atom slow release in reaction process is controlled so as to obtain 2-amino-5-chloropyridine. Basically no side reaction is induced, methanol and active carbon are adopted for decolouring refining, the obtained product is subjected to chromatogram determination, and the purity is as high as about 99.8%. The reaction steps of the preparation method are simple; the preparation method is easy to control; no organic reagent such as ethanol is adopted as a reactionreagent; three wastes discharge is reduced; and product purity and quality are improved.