The invention relates to a synthesis method of 3-methoxyl-N, N-dimethylacrylamide, and belongs to the technical field of chemical synthesis. The synthesis method comprises the following steps of adding 3-methoxypropionic acid and dimethylamine into a sealed reactor; raising the temperature to 80 to 150 DEG C; performing reaction to obtain 3-methoxyl-N, N-dimethylacrylamide, wherein the pressure in the sealed reactor is 0.1 to 10.0MPa. The 3-methoxypropionic acid is used as the raw materials to perform high-temperature dewatering with dimethylamine in a sealed reaction vessel; polyhydric alcohol and basic catalysts are not needed; the reaction is simple; the implementation is easy; the yield of a product is high; the purity is high; the high yield is realized; meanwhile, the pollution is little; the cost is low; the method conforms to the requirements of modern chemical green synthesis. Meanwhile, the 3-methoxypropionic acid uses low-price acrylonitrile as the starting raw materials; the acrylonitrile is subjected to alkoxylation to obtain methoxyl propionitrile; then, hydrolysis is performed. The operation is simple; the energy consumption is low.