The invention provides a feed additive for promoting emotional calmness of swine and a preparation method and application of the feed additive. The feed additive is prepared from the raw materials: beta-alanine, isoleucine, vitamin C and optional carriers. According to the feed additive for promoting the emotional calmness of the swine and the preparation method and application of the feed additive, compatibility use of the beta-alanine, the isoleucine and the vitamin C is carried out, the effects of reducing the excitement degree of the swine and reducing the stress degree of the swine can beachieved, a function of inhibiting fighting and tail biting is achieved, and the weight increment effect can be improved.