The invention belongs to the technical field of chemistry, and particularly relates to a synthetic method of an azithromycin rearrangement impurity R. The method mainly comprises the steps that (3R,4R,5S,6R,9R,10S,11S,12R,13R,15R,Z)-12-[[3,4,6-trideoxy-3-(dimethylamino)-beta-D-wood-pyranose group]oxygen]-6-ethyl-4,5-dihydroxyl-10-[(2,6-dideoxy-3-C-methyl-a-L-nuclear-pyranose group)oxygen]-3,5,9,11,13,15-hexamethyl-7,16-dioxy-2-azabicyclo[11.2.1]cetane-1-alkene-8-ketone(compound III) is subjected to acidification rearrangement, and after refining is conducted, the rearrangement impurity R withthe purity being 99.5% or above is obtained. The synthesized high-purity azithromycin rearrangement impurity R serves as an impurity standard substance of finished production detection, locating and qualification on the impurity are enhanced conveniently, and quality control over azithromycin active pharmaceutical ingredient is improved.