The present invention discloses an animal feed yeast body protein and a preparation method thereof; the animal feed yeast body protein comprises candida utilis, candida tropicalis, torulopsis torulopsis, saccharomyces cerevisiae, a mixed additive, and water added to 1g as a supporter; wherein in more than 1800 strains of the three types of strains, a strain biochemical experiment and a strain symbiosis experiment are carried out, thereby selecting the microorganisms and preparing a yeast suspension. According to the present invention, the variety, the digestive tract microflora and the physiological digestion characteristics of animals are fully paid attention to, and the rich functional factors can improve the gastrointestinal function and the immune function of the animals, so that the animal feed yeast body protein is rich in B vitamins, organic trace elements, enzymes, small peptides, organic acids and other various yeast metabolites. The product can improve the digestion utilization rate of the feed, improve the production performance and reduce the production cost. Therefore, the feed digestion and utilization rate is increased, the disease resistance of the organism is enhanced, and the mycoprotein is high-quality mycoprotein which is very suitable for pigs, poultry, cattle and aquatic animals.