The invention discloses a synthesis method of light stabilizer N,N-bis-(2,2,6,6-tetramethyl-4-piperidyl) isophthalamide. Isophthaloyl dichloride and 2,2,6,6-tetramethyl-4-piperidyl are taken as raw materials and react in the presence of a catalyst and a solvent, and N,N-bis-(2,2,6,6-tetramethyl-4-piperidyl) isophthalamide is prepared. According to the synthesis method of the N,N-bis-(2,2,6,6-tetramethyl-4-piperidyl) isophthalamide, the separation and purification process is simple, the reaction time is short, the product yield can be higher than 96%, the product purity is higher, the energy consumption is low, the environmental pollution is small, the cost is low, and the method is a more ideal process for industrial production.