An electrolytic synthesis method of 3,6-matrigon takes alkaline aqueous solution as the reacting medium, which comprises the following step: dissolving 3,4,5,6-tetrachloropicolinic acid or the salt of the 3,4,5,6-tetrachloropicolinic acid in the alkaline aqueous solution, proceeding the electrolytic reducing reaction, obtaining target compound (II) after the electrolytic reaction and the acidification, wherein, firstly, proceeding the electrolytic reaction in the alkaline aqueous solution system with pH value 8.5-11, secondly, continuingly completing the electrolytic reaction under condition of the alkaline range is between pH value 13 and pH value 13.5 after obtaining trichloropyridine formate intermediate compound (I). The method has the advantages of easy operation, safety, friendly to the environment, the reaction temperature of the first stage can reach over 80 DEG C, the dissolvability of the reactant is efficiently improved, the reaction velocity is quickened, the batch output of the products is increased, and the spurging and the hydroxylating secondary reaction are efficiently avoided.