Feed additive capable of remarkably improving production performance of pregnant sows and pig house environment and use method of feed additive

The invention relates to a feed additive capable of remarkably improving the production performance of pregnant sows and the pig house environment and a use method of the feed additive, the feed additive is prepared from saccharomycetes, lactobacillus acidophilus and bacillus subtilis according to the mass ratio of 1: (0.8-1.2): (0.8-1.2), and the viable count is larger than or equal to 1.1 * 10 CFU/g. The feed additive is added into a basic ration at the later period of pregnancy of the sows to serve as a special feed for the pregnant sows, and the live litter number, the healthy litter number, the newborn litter weight and the weaning litter weight of the pregnant sows can be remarkably increased; the immunity of the pregnant sows is improved, and the IgG and IgM levels in colostrum of the pregnant sows are improved; and the concentrations of ammonia gas, carbon dioxide and PM2.5 in a pregnant sow house are obviously reduced. According to the special feed added with the feed additive for the pregnant sows,