A synthesis method of 3-methylamino-1,2-propanediol is disclosed in the invention, and it includes the following steps: (a) adding glycerin chlorohydrin, aqueous monomethylamine solution and an amination catalyst, namely NaOH solution and NaHCO3, into a reactor, mixing the material sufficiently, and allowing amination reaction to proceed in two temperature stages; (b) removing monomethylamine and water from the amination solution after the amination reaction is completed, filtering out the solid resultant, and feeding the filtrate into a still; (c) distilling under reduced pressure to obtain 3-methylamino-1,2-propanediol, wherein the vacuum for distillation under reduced pressure is equal to or greater than 0.099 MPa and the temperature is 130-160° C.