The invention discloses a method for improving the preparation technology of 3-(2,2-dimethylhydrazino)methyl propionate and 3-(2,2,2-trimethylhydrazino)methyl propionate. The 3-(2,2-dimethylhydrazino)methyl propionate and 3-(2,2,2-trimethylhydrazino)methyl propionate are intermediates of a mildronate bulk drug. In the prior art, the intermediates are prepared by the following steps: making 1,1-dimehtylhydrazine carry out reactions with methyl acrylate, and then subjecting the reaction products to methylation reactions so as to obtain the target products; but the conventional technology has the disadvantages that the quality and stability of the obtain products are bad, thus the technology for producing the mildronate bulk drug becomes more complicated, and the synthesis cost is increased. The provided method separates two reactions in the synthesis route, exothermic reaction material feeding automatic control of each reaction is realized under mild conditions, the final products are subjected to a primary cooling precipitation and a secondary special purifying technology so as to obtain high purity products without complicated steps like recrystallization and washing, moreover the stability and yield of the products are both improved, the treatment time is shortened, the shelf life of the products is prolonged from two years to four years, and the method can be applied to commercial massive production.