The invention belongs to the technical field of petrochemical engineering and particularly relates to an inclusion type long-acting deoxidant for a drilling fluid and a preparation method. The long-acting deoxidant is prepared from raw materials in parts by mass as follows: 10-15 parts of inclusion bodies, 10-15 parts of polyphenol catalysts, 3-12 parts of an active ingredient A of a hydroxylaminecompound, 3-12 parts of an active ingredient B of a hydroxylamine compound and 50-65 parts of a solvent. The problems that deoxidants in the prior art are not compatible with drilling fluids, the performance of the drilling fluids is affected or the long-acting deoxidization of a non-closed system in the circulating process of the drilling fluids cannot met are solved, the long-acting deoxidant controls slow release of a catalyst in a solution, continuously catalyzes a hydroxylamine compound strong oxidizer and dissolved oxygen in the drilling fluids to be subjected to a rapid reaction and achieve the purposes of enhancing the deoxidization effect and prolonging the deoxidization timeliness.