The invention provides a feed additive for controlling recessive mastitis of a cow and reducing somatic cells and a preparation method thereof. The feed additive comprises Chinese herbal medicines, vitamins, minerals and probiotics and concretely, comprises 100 to 150g of licorice root, 50 to 100g of radix angelicae sinensis, 80 to 120g of radix astragali, 80 to 120g of pericarpium citri reticulatae, 50 to 100g of dandelion, 80 to 100g of fructus arctii, 50 to 100g of ligusticum wallichii, 100 to 150g of motherwort, 50 to 80g of Chinese violet, 60 to 100g of seed of cowherb, 50 to 80g of acanthopanax root, 50 to 80g of myrrh, 50 to 80g of white paeony root, 80 to 120g of honeysuckle, 80 to 120g of Houttuynia cordata, 50 to 100g of red sage root, 50 to 100g of pilose asiabell root, 30 to 50g of vitamin A (500000 IU / g), 20 to 30g of vitamin D3, 30 to 50g of vitamin E (5000000 IU / g), 150 to 200g of zinc hydroxymethionine, 10 to 20g of yeast selenium, 80 to 120g of saccharomycetes (20 billion cfu / g) and 10 to 20g of Bacillus licheniformis (20 billion cfu / g). The feed additive can improve the physiological functions of dairy cows, reduce the incidence of mastitis, improve the anti-oxidant capacity, reduce somatic cells and improve the quality of milk.