The invention relates to the technical field of pharmaceutical intermediates, in particular to a preparation method of 3-(N-methyl-N-phenyl)aminoacrolein. The preparation method comprises the following steps that tetramethoxypropane and N-
methylaniline are put into a reaction flask, and after stirring is conducted for 10 min, diluted
hydrochloric acid is dropwise added; after diluted
hydrochloric acid is dropwise added completely, stirring is conducted for 2.5 h at the temperature of 24 DEG C to 26 DEG C; methylbenzene is added, and caustic soda liquid is dropwise added at 30 DEG C or below to regulate the pH value to be 6-7; standing is conducted for layering, a
water layer is extracted with methylbenzene, organic
layers are mixed, and washing is conducted three times with a saturated
salt solution; standing is conducted for layering, a
solvent in the
organic layer is recycled by reducing pressure, 60-70-DEG C 40-mmHg distillates are collected, and then the product is obtained. According to the preparation method, expensive N-methylformanilide, n-
butyl vinyl ether and
propargyl alcohol are not used as raw materials, and therefore the cost is reduced; due to the fact that conventional solvents such as
acetonitrile and
chlorobenzene and poisonous substances such as
triphosgene are not used, three waste
pollution is reduced, and the reaction yield is increased; in the synthesis process, reacting is conducted at the environment temperature, the operation process is simplified,
impurity generation is reduced, the quality of the product is improved, and the reaction yield is increased.