The invention relates to a preparation method of a mixed feed for livestock and poultry. The every 100 g of mixed feed is prepared from the following ingredients by weight: 2 g of tea, 3 g of pine needle, 10 g of oil tea cake meal, 1 g of lactuca sativa leaf powder, taxus chinensis var mairei, 50 g of corn, 20 g of wheat bran, 19 g of soybean meal, 1 g of calcium, 1 g of bone meal and 1 g of salt, green feed is matched with tea, taxus chinensis bark and pine needle, energy feed is matched with corn, wheat bran and soybean meal, protein feed is matched with oil tea cake, and root block feed is matched with calamus sweet potatoes and the like. The physique immunity function of livestock and poultry can be enhanced through the tea, white blood cells can be increased, so that the effects of resisting cancer, preventing cancer and preserving health are achieved, the pine needle leaf powder can adjust the organism functions of the livestock and poultry, the disease resistance rate can be increased, the laying rate can be increased, the oil tea cake can make the raised livestock and poultry high in disease resistance and good in meat quality, the lactuca sativa leaf powder has the effect of preventing digestive tract diseases, and the bark, branches, leaves and seeds of taxus chinensis var mairei contain taxol, so that the taxus chinensis var mairei can treat various cancers, and belongs to a good anti-cancer and cancer-preventing medicine.