The invention relates to the field of animal feed additive, in particular to a feed additive for improving immunity for beasts and birds. The feed additive comprises the following components in weight portion: 2 to 5 portions of spirulina powder, 1 to 3 portions of milk veteh, 1 to 3 portions of radix codonopsitis, 1 to 5 portions of forsythia, 3 to 7 portions of purslane, 0.4 to 1 portion of honeysuckle, 0.2 to 0.5 portion of licorice, 1 to 5 portions of calcium biphosphate and 0.01 to 0.05 portion of citric acid. The spirulina powder, the milk veteh, the radix codonopsitis, the forsythia, the purslane, the honeysuckle and the licorice are subjected to superfine grinding, filtered by a shaking screen with 100 to 200 meshes, and then mixed with calcium biphosphate powder and citric acid powder, stirred evenly, sterilized, cooled, and packaged to obtain the feed additive. The feed additive is a pure natural traditional Chinese medicine preparation, has no medicament residue and no toxic and side effects after long-term use, enhances the immunity of organisms, can obtain the bird egg products in accordance with export standard after the birds eat the feed additive, does not generate medicament resistance, has low raw material cost, and is suitable for industrial volume production.