The present invention relates to a method for synthesizing N,N′-bis(2,2,6,6-tetramethyl-4-piperidyl)-1,3-benzenedicarboxamide as shown in the following formula (III), comprising the following steps that a compound of the following formula (I) and a compound of the following formula (II) react under stirring in an organic solvent in the presence of a solid supported catalyst, and after the completion of the reaction, a compound of the formula (III) is obtained by post-treatment, wherein R1 to R2 are each the same or different selected from C1-6 alkyl. The method can achieve good technical effects through the use of a unique catalyst and the compounding of the organic solvent, has the advantages of reduced pollution, good environment and significant improvement on yield compared with the prior art, can provide more inexpensive functional additives for the field of plastic processing, and has good industrial production prospects and application potential.