A kind of preparation method of mecobalamin

The invention provides a kind of preparation method of mecobalamin; comprise: under high pure nitrogen protection; use aprotic polar solvent as reaction solution; methylation reaction reagent is added to carry out methylation reaction to vitamin B12 under the effect of highly basic; under low temperature, add frozen water after completion of the reaction has a large amount of solid to separate out, and separates out product and carries out obtaining mecobalamin after chromatographic separation through chromatography column.The preparation method of disclosed mecobalamin has simple to operate, and preparation cost is low, is easy to realize suitability for industrialized production, and the list in finished product is mixed and always mixed less.