The invention belongs to the technical field of medicinal chemistry, and particularly relates to a synthesis method of metroprolol succinate ortho-isomer impurities. The synthesis method comprises thesteps: the metroprolol succinate ortho-isomer impurities are prepared by taking salicylaldehyde as a raw material through four steps of reactions, namely the Wittig reaction, the reduction hydrogenation reaction, the substitution reaction and the ring-opening reaction. The synthesis method of the metroprolol succinate ortho-isomer impurities totally includes the four steps of reactions, the raw material is easy to obtain, the total yield is greater than 40%, and contribution is made to strictly control the content of the metroprolol succinate ortho-isomer impurities through an external standard method; and the synthesis method of the metroprolol succinate ortho-isomer impurities is easy to operate, mild in reaction, high in product purity and suitable for drug quality study.