The invention relates to a synthesis method of azepine anthraquinone. The azepine anthraquinone is obtained by carrying out intramolecular 6-endo-dig cycloisomerisation reaction shown as in formula (1) on N-propargyl quinine with a 1,5-eneyne structure under the action of a metal catalyst, and purifying, wherein the intramolecular 6-endo-dig cycloisomerisation reaction is homogeneous phase metal catalytic reaction, the metal catalyst is gold salt, platinum salt or univalent gold complex; and the use level of the metal catalyst is 0.01-0.5 equivalent weight of the N--propargyl quinine. The gold slat is auri chloridum (AuCl3) or aurous chloride (AuCl); the platinum salt is platinum tetrachloride, platinum bichloride or potassium chloroplatinate; and the univalent gold complex is PPh3AuOTf, PPh3AuSbF6, PPh3AuNTf2 or LAuNTf2, wherein L is nitrogen heterocyclic ring carbene ligand. The invention realizes the synthesis of the azepine anthraquinone by utilizing metal catalytic intramoleculareneyne cyclization reaction, and has the advantages of simple and easy-accessible raw materials and moderate reaction conditions.