Method for producing metformin hydrochloride from complex solvents

The invention discloses a method for producing metformin hydrochloride from complex solvents. The method comprises the steps of dimethylamine hydrochloride preparation and metformin hydrochloride preparation, wherein the metformin hydrochloride preparation comprises the steps of adding raw materials and solvents, heating and warming, cooling, cooling secondarily, centrifuging, washing, crystallizing and drying; the heating and warming comprises the steps of introducing steam into an addition kettle jacket, heating, adjusting a stirring rotation speed to be 80 to 130 turns per minute, warming 30 to 50 minutes to raise kettle temperature to 110 to 115 DEG C, keeping 10 to 30 minutes, continuously warming 15 to 30 minutes to raise temperature to 118 to 125 DEG C and keeping warm to react for 1.5 to 2.5 hours. In the metformin hydrochloride preparation, double components of dimethyl formamide and ethylene glycol monopropyl ether are utilized as the solvents, the metformin hydrochloride can be prepared by using a synergistic effect of two solvents with different characters, product yield is greater than 95%, and purity is greater than 99.90%.