The invention discloses a synthesis method of retigabine. The synthesis method comprises the following steps: dissolving N-(2-nitro-4-aminophenyl) ethyl carbamate in an organic solvent, dropping p-fluorobenzaldehyde, stirring for reaction to ensure that a product is not separated, and directly adding a metal hydroboron for reducing to obtain an intermediate N-[2-nitro-4-(4-fluorophenyl methyl amino) phenyl] ethyl carbamate; and dissolving the intermediate N-[2-nitro-4-(4-fluorophenyl methyl amino) phenyl] ethyl carbamate in an alcohols solvent, and performing ferric iron compound/ hydrazine hydrate catalytic transfer hydrogenation to obtain the retigabine. The synthesis method has the advantages of mild reaction conditions, simplicity and convenience in operation, high yield of products, good quality, low cost and environmental friendliness, and is suitable for industrialized production.