The invention belongs to the technical field of medicines and relates to a method for continuously preparing
argatroban. The method comprises the specific processes of achieving N-nitro-L-
arginine sulfonylation reaction through a
phase transfer catalyst in two phases of water and a
solvent; after reaction is completed, directly carrying out condensation on an organic phase without concentration treatment and ethyl (2R,4R)-4-methyl-2-piperidinecarboxylate; after reaction is completed, carrying out
hydrolysis reaction on a water phase in an alkaline condition; carrying out hydrogenation reduction by using a
microreactor; and finally carrying out refining to obtain
argatroban. According to the method, tedious treatment and purification steps of various intermediates are reduced, and
continuous reaction is achieved, so that the production efficiency is improved. Meanwhile, almost the same
solvent is adopted by a plurality of steps in the reaction process,
solvent recovery is facilitated, and the target of waste liquid reduction is achieved. In addition, the
microreactor is adopted by the method for carrying out
palladium carbon hydrogenation reduction, so that high temperature,
high pressure, long reaction time and other problems in the
hydrogenation process are avoided to ensure the safety in the production process.