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This invention discloses a method for synthesizing an intermediate of retinoic acid, relating to the field of pharmaceutical organic synthesis technology, comprising the following steps: S1, in the presence of a base, 2-amino-3-chloropyridine and 4-bromopiperidine undergo a nucleophilic substitution reaction in solvent A to prepare compound III; S2, in the presence of a catalyst and ammonia solution, compound III undergoes an amination reaction in solvent B to prepare compound II; S3, compound II is dissolved in solvent C, and sequentially undergoes CDI cyclization and hydrogen chloride solution salt formation to prepare compound I, namely 1-(piperidin-4-yl)-1,3-dihydro-2H-imidazo[4,5-b]pyridin-2-one. This invention is low-cost, uses mild reaction conditions, has a simple synthesis process, high yield, and eliminates the need for expensive and potentially unsafe excipients, effectively improving reaction safety, being environmentally friendly, and suitable for industrial production.