The invention discloses a preparation method of malonate, which uses chloroacetic acid as a raw material to carry out neutralization reaction, cyanation reaction, alkali hydrolysis reaction, dehydration, acidification reaction, re-dehydration and esterification reaction, and is characterized in that: acidification reaction, further Dehydration and esterification reaction process. The acidification reaction refers to the reaction of sodium malonate and acid in the alkali hydrolysis reaction solution to generate malonate and sodium salt, after the reaction is completed, the undissolved inorganic salt is filtered and separated, and the filtrate is vacuum concentrated and dehydrated to obtain a malonate mixed salt; Esterification refers to the esterification of malonic acid mixed salt with alcohol, water-carrying agent and sulfuric acid to prepare malonate. The preparation method of malonate provided by the invention can make the conversion rate of esterification reaction up to more than 92%, and the product yield can reach more than 85%. The reaction conditions are mild, the process flow is short, the operation is simple, safe, environmentally friendly, easy to implement, and low Low, easy to industrial production, has high application value.