The invention discloses a feed additive capable of improving anti-stress and immunity of ruminants and a preparation method thereof. The feed additive capable of improving the anti-stress capability and immunity of ruminants is prepared from the following raw materials: bacillus subtilis powder, lactobacillus plantarum powder, saccharomycete powder, catechuic acid, xylooligosaccharide, calcium fatty acids, chromium nicotinate, medical stone, vitamin C, vitamin B1, nicotinic acid, pine pollen, tricalcium phosphate, manganese sulfate, soy isoflavone, berberine, soya bean meal, versioolor swallowwort root, herba ephedra, futokadsura stem, herba potentillae chinensis, ford manglietia fruit, ciliate desert-grass, ajuga decumbens, tangerine leaves, cow soapwortseed and table salt. The feed additive capable of improving the anti-stress capability and immunity of ruminants contains multiplex vitamins, trace elements and Chinese medicinal herb ingredients, and all the ingredients achieve a synergistic effect, so that the intestinal micro-ecological environments of ruminants can be effectively improved, the quantity of pathogens is reduced, stress reaction is reduced to a great extent, the immunity is improved and thus the disease incidence of ruminants.