The present invention relates to a meat quality improving feed additive for fattening pigs and a preparation method and an application thereof, and belongs to the field of feed. The feed additive comprises 20-40 parts by weight of creatine monohydrate, 5-25 parts by weight of alpha-lipoic acid, 2-10 parts by weight of carnosine, 2-10 parts by weight of yucca extract and 15-71 parts by weight of carriers. The preparation method comprises the following steps: the carnosine, yuccan extract and carriers are mixed, then the creatine monohydrate and alpha-lipoic acid are added, and the materials are continuously mixed to obtain the finished products. The preparation method is simple and the preparation condition is good in controllability. The prepared feed additive by the method can slow down pH of muscles of the fattening pigs, increases water holding capacity of the muscles, improves meat color and tenderness, can be applied in the feed for the fattening pigs, can significantly improve the meat quality and flavor of the fattening pigs, at the same time improves antioxidant capacity of the fattening pig body and reduces ammonia nitrogen emission.