The invention discloses coated granules containing natural oregano oil for birds and a preparation method thereof. The coated granules can effectively improve stability, ingestion convenience and bioavailability of oregano oil as feed additives. The technical scheme is that granular silicon dioxide or calcium carbonate is used as a core material, starch, beta-cyclodextrin and microcrystalline cellulose are used as a coated layer, a groove mixing blender is used for fully mixing the core material and the coated layer to manufacture the granules, and after the granules are dried, oregano oil is sprayed onto the granules to obtain the coated granules. Absorbing capacity of the core material of the silicon dioxide or the calcium carbonate on oregano oil is weak, the birds can eat the granules conveniently, after the granules are eaten, on the one hand, an effect of helping mechanical digestion is obtained, and on the other hand, releasing of oregano oil is not affected. The starch, beta-cyclodextrin and microcrystalline cellulose of the coated layer have a good clathration effect on the oregano oil, and the granules can be placed stably for a long time.