The invention discloses a method for synthesizing adenine represented by a formula (I), wherein the method comprises the following steps of making formamide react with diethyl malonate in an ethanol solution of sodium ethoxide to obtain a raw material 4,6-dihydroxypyrimidine represented by a formula (VI); nitrifying the 4,6-dihydroxypyrimidine to obtain 4,6-dihydroxy-5-nitropyrimidine represented by a formula (V); carrying out chlorination reaction on the 4,6-dihydroxy-5-nitropyrimidine (V) to obtain 4,6-dichloro-5-nitropyrimidine represented by a formula (IV), carrying out aminolysis reaction on the 4,6-dichloro-5-nitropyrimidine (IV) and an saturated aminoethanol solution to obtain 4,6-diamino-5-nitropyrimidine represented by a formula (III); carrying out catalytic hydrogenation on the 4,6-diamino-5-nitropyrimidine (III), and reducing a nitro group to obtain 4,5,6-triaminopyrimidine represented by a formula (II); making the 4,5,6-triaminopyrimidine (II) react with ethyl orthoformate in acetic anhydride to obtain the adenine represented by the formula (I). The method provided by the invention has the advantages of cheap and easily-obtained raw materials, mild reaction conditions, single product, high total yield, low production cost and easiness in industrial production.