The invention discloses a preparation method of 3-(2,2,2-trimethylhydrazine)
propionate dihydrate, belonging to the technical field of 
chemical synthesis. The method comprises the following steps: adding tert-
butyl acrylate into a three-neck flask with a mechanical stirring and 
dropping funnel, dropwisely adding excessive 5-50% 
unsymmetrical dimethylhydrazine, and distilling out 3-(2,2-
dimethylhydrazine)tert-butyl 
propionate while depressurizing; dissolving the 
distillation product in 
ethanol, introducing or dropwisely adding excessive 5-30% 
methylation reagent, and washing with cold 
ethanol to obtain 3-(2,2,2-trimethylhydrazine)tert-butyl 
propionate; dissolving the 3-(2,2,2-trimethylhydrazine)tert-butyl propionate in water, adding a small amount of acid, and heating under 
reflux for 1-3 hours; depressurizing to remove water and acid; and adding 
solvent and organic amines into the remainder, filtering, and recrystallizing the 
solid with 95% 
ethanol to obtain the target product. The invention converts the 
alkaline hydrolysis in the prior art into acidic 
hydrolysis and consumes less acid, and the acid can be removed by depressurized 
distillation; and the 
neutralization only needs a small amount of alkali, and the salt generated after 
neutralization can be dissolved in the 
solvent so as to be removed, so that the purity of the obtained product is high.