Abstract: The present invention relates to a method for preparing an X-ray contrast agent iomeprol and, more specifically, to a method for preparing iomeprol by adding an inorganic base, an inorganic chloride, a solvent, etc. to 5-(2-hydroxyacetamido)-N,N?-bis(2,3-dihydroxypropyl)-2,4,6-triiodoisophthalamide (1b) to cause N-methylation reaction, thereby enabling easy separation and removal of inorganic salts generated during the reaction, without treatment with an ion exchange resin, while reducing the conventional production time, and minimization of the amount of reaction impurities.