The invention relates to a synthesis method of 2-chloro-1-(2, 2-dimethyl-4H-benzo [1, 3] dioxin-6-yl) ethanone, the method comprises the following steps: (1) carrying out hydroxymethylation on methyl 4-hydroxybenzoate to obtain methyl 4-hydroxy-3-(hydroxymethyl) benzoate; (2) carrying out acetonylidene protection on ortho-dihydroxyl of the 4-hydroxy-3-(hydroxymethyl) methyl benzoate, so as to obtain 2, 2-dimethyl-4H-benzo [d] [1, 3] dioxin-6-carboxylic acid methyl ester; and (3) carrying out chloromethylation on the 2, 2-dimethyl-4H-benzo [d] [1, 3] dioxin-6-carboxylic acid methyl ester, so as to obtain the 2-chloro-1-(2, 2-dimethyl-4H-benzo [d] [1, 3] dioxin-6-yl) ethanone. The synthesis route does not involve a Friedel-Crafts acylation reaction, liquid bromine does not need to be used, the initial raw materials belong to bulk chemicals, the synthesis route is short, the synthesis route is safer and more environmentally friendly, and mass production of the 2-chloro-1-(2, 2-dimethyl-4H-benzo [1, 3] dioxin-6-yl) ethanone is easy to achieve.