The invention belongs to the technical field of medical intermediates, and particularly relates to a preparation method of 2-(5-bromine- 3-methylpyridine-2-yl) acetic acid hydrochloride. According tothe preparation method, n-butyllithium and acetonitrile are subjected to a reaction so as to increase protection of bromine in a compound A, and then the compound A is added for a reaction so as to form a compound B so that the yield and the purity of the product are improved, side reactions are avoided, and the compound B and concentrated hydrochloric acid are subjected to a reaction, and the 2-(5-bromine-3-methyl pyridine-2-yl) acetic acid hydrochloride with high purity and high yield is obtained; the synthetic route of the 2-(5-bromine-3-methyl pyridine-2-yl) acetic acid hydrochloride is short, the design is reasonable, the operation is simple, the control is easy, and the product yield is higher.