The invention relates to the technical field of hydrate inhibitors used for well drilling fluids, and especially relates to a hydrate inhibitor based on an ionic liquid and used for a well drilling fluid. The hydrate inhibitor is based on the pyridine ionic liquid, polymeric alcohol is added in an ionic liquid synthetic process, and therefore a pyridin-polymer complex is formed, a hydrate generation temperature can be effectively reduced, and the usage amount of the hydrate inhibitor is reduced at the same time. The hydrate inhibitor based on the ionic liquid and used for the well drilling fluid comprises the following components, in percent by mass: 20-25% of halogenated n-alkanes, 15-20% of pyridine (C5H5N), 5-10% of aniline hydrochloride (C6H5NH2.HCl), 10-15% of sodium fluoroborate (H4BF4N), and 32-45% of polyethylene glycol.