Methylaminoformyl chloride is prepared by reacting methylamine with phosgene. Reaction equation: CH3NH2+COCl2→CH3NHCOCl. A 40% aqueous solution of methylamine is vaporized, and after drying, it is combined with phosgene at a ratio of 1:1.3 (methanol), methylamine at 4 m3/h, and phosgene at a rate of 8.6 m3/h (content 60%-70%). Preheating into the preheater, the preheating temperature of methylamine is controlled at 220-260°C, and the phosgene is controlled at 200-240°C. The preheated two gases enter the test tube and are synthesized at 280-300°C to obtain gaseous methaqualyl chloride. Then, carbon tetrachloride (or chlorobenzene solution) is circulated and absorbed at 0-20°C to obtain a solution of about 10% of carbamoyl chloride (or chlorobenzene), or cooled to a liquid product after 35-40°C or lower[2,3].