TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The catalyst in chlorination is sulfur trioxide, boron trichloride, ferric trichloride or aluminum trichloride. The inorganic alkali compound is hydroxide of alkali metal, carbonate of alkali metal, bicarbonate and acetate. The metal catalyst in hydrogenation is mono-metal catalyst, poly-metal catalyst and load or non-load type metal catalyst. The hydroxide of alkali metal is sodium hydroxide or potassium hydroxide. The carbonate or bicarbonate of alkali metal is sodium carbonate, potassium carbonate, sodium bicarbonate and potassium bicarbonate. The mono-metal catalyst is platinum, palladium, cobalt or nickel. The poly-metal catalyst is binary alloy catalyst copper-nickel, copper-palladium, palladium-silver, platinum-gold or platinum-copper. The load type metal catalyst is platinum carbon or palladium carbon. The non-load type metal catalyst is raney nickel, raney copper or raney cobalt. The metal catalyst is platinum carbon, palladium carbon, raney nickel and raney copper. The inorganic acid is hydrochloric acid, sulfuric acid, carbonic acid, phosphoric acid or nitric acid    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The dosage of catalyst is 0.01-1 (preferably 0.01-05) times of mol dosage of 2,6-dichloropyridine. The chlorination is performed at 100-200 degrees C. The low-concentration rectified solution produced in rectification process in chlorination can be further used for next reaction or rectifying and extracting in next reaction. The acid binding agent in hydrogenation is organic alkali or inorganic alkali compound. The organic alkali compound is pyridine, triethylamine, alkali metal salt of alcohol, metal alkyl lithium compound or amido lithium compound. The organic dissolvent in hydrogenation is ester, ether, aromatic hydrocarbon and nitrile. The alkali metal salt of alcohol is sodium methoxide, potassium ethoxide and potassium tert-butoxide. The metal alkali metal lithium compound is butyl lithium or phenyl lithium. The amido lithium compound is diisopropyl amido lithium or hexamethyl disiloxane amido lithium. The acetate is sodium acetate or potassium acetate. The ester is methyl acetate, ethyl acetate or butyl acetate. The ether is diethyl ether, methyl butyl ether, tetrahydrofuran or para-dioxane. The arene is benzene, methylbenzene or chlorobenzene. The nitrile is acetonitrile or propionitrile. The acid binding agent is pyridine or triethylamine. The organic dissolvent is methylbenzene or ethyl acetate. The pressure in hydrogenation is 0-5 MPa. The reaction temperature in hydrogenation is 20-150 degrees C. The mol ratio of 2,3,6-trichloropyridine to acid binding agent in hydrogenation is 1:0.7-1. The filtered catalyst can be recycled for future use after hydrochloride is dissolved with water in the post-treatment. The organic dissolvent layer in post-treatment can be fed with 2,3,6-trichloropyridine and organic dissolvent to be recycled as next batch of raw material. The water-containing acid in post-treatment is inorganic acid or organic acid capable of being dissolved into water. The organic acid is formic acid, acetic acid, propionic acid, n-butyric acid or pentanoic acid. The mol. ratio of the water-containing acid to 2,3,6-trichloropyridine is 1-5:1. The organic acid can be also selected from salicylic acid or benzenesulfonic acid.