The invention provides a growing-finishing pig feed additive capable of effectively enhancing the immunologic function and improving the pork quality of a growing-finishing pig. The feed additive comprises the following compositions: selenium yeasts, Tremellan, cysteamine, sodium butyrate, phytase, arginine, 50% choline chloride, and the balance of carrier mountain flour, powdered zeolite or medical stones. The feed additive provided by the invention has the advantages that in case of adding the feed additive into feeds for feeding growing-finishing pigs, the lean meat rate of the growing-finishing pig can be obviously increased so as to enable the pork thereof to be ruddy and delicate, the meat flavor of the growing-finishing pig can be improved, and the consumer demands can be satisfied; meanwhile, the Tremellan can effectively improve the pork quality, improve the eye muscle area, and reduce the backfat thickness, intramuscular fat content and drip loss of the pork; through adding the Tremellan and the selenium yeast into the basic ration, the anti-stress capability of the growing-finishing pig can be enhanced, and the appearance rate of PSE meat can be reduced; and the pork quality of the growing-finishing pig is improved, the intestinal bacterial colony of animals is improved, the immune level of the growing-finishing pig is improved, and then a new growing-finishing pig feed formula is provided for actual production, thereby stabilizing the feed quality, and increasing the breeding effect.