Method for recovering and preparing dabigatran etexilate mesylate from production mother liquor

The invention provides a method for recovering and preparing dabigatran etexilate mesylate from production mother liquor, and relates to the technical field of preparation of dabigatran etexilate mesylate. The method specifically comprises the following steps: carrying out reduced pressure distillation on the dabigatran etexilate mesylate production mother liquor until the weight is constant, sequentially adding acetonitrile, a pH regulator and purified water into an obtained solid mixture, and carrying out cooling crystallization to obtain dabigatran etexilate free alkali; then adding ethyl acetate, purifying and crystallizing to obtain refined dabigatran etexilate free alkali; the method comprises the following steps: dissolving refined dabigatran etexilate free alkali in acetone, salifying with methanesulfonic acid to prepare dabigatran etexilate mesylate, crystallizing, and finally further refining the dabigatran etexilate mesylate through an alcohol-acetone system to obtain a high-quality dabigatran etex