The invention discloses 1,6-diisocyanatohexane modified bisphenol A formaldehyde phenolic resin and a synthetic method thereof. According to the resin provided by the invention, 1,6-diisocyanatohexaneis grafted onto bisphenol A formaldehyde phenolic resin to form a strong-flexibility polyurethane group, so that the brittleness of the bisphenol A formaldehyde phenolic resin is improved, and the modified 1,6-diisocyanatohexane modified bisphenol A formaldehyde phenolic resin has stronger flexibility and a high molecular weight, high adhesion, high acid and alkali resistance, high strength and high elasticity modulus of the raw material bisphenol A formaldehyde phenolic resin; the synthetic method uses the 1,6-diisocyanatohexane as a grafting monomer and dibutyltin dilaurate as a catalyst, the 1,6-diisocyanatohexane is subjected to grafting under the action of the catalyst to form the strong-flexibility polyurethane group, so that the bisphenol A formaldehyde phenolic resin with inherentrigidity and the 1,6-diisocyanatohexane are compounded, and the flexibility softness is increased; and the whole preparation process is relatively simple and convenient and prone to industrialized promotion