The invention belongs to the field of chemical pharmacy, and specifically relates to a method for synthesizing lenvatinib. The method comprises the following steps: step 1, taking 4-aminosalicylic acid as a raw material, and preparing 4-chloro-7-methoxyquinoline-6-formamide through methylation, condensation with meldrum's acid, high-temperature cyclization, chlorination and ammoniation; step 2, taking 3-chloro-4-aminophenol as a raw material, and reacting with phenyl chloroformate and cyclopropylamine to obtain 1-(2-chloro-4-hydroxy phenyl)-3-cyclopropyl urea; and step 3, enabling the 4-chloro-7-methoxyquinoline-6-formamide prepared in step 1 to react with the 1-(2-chloro-4-hydroxy phenyl)-3-cyclopropyl urea prepared in step 2 under action of potassium tert-butoxide to obtain the lenvatinib. The invention provides a brand-new route for synthesising the lenvatinib. The used reagent is cheap and is easily available, is simple in operation, has a yield higher than that of other methods, and is easy for industrial production.