L-Tryptophan is one of the eight essential amino acids in the life activities of human body and animals, it exists in the organism in free state or combined state, it plays a very important role in the growth and development, metabolism of human beings and animals, it is known as the second essential amino acid, it is widely used in many aspects such as medicine, food and feed, etc. L-Tryptophan is one of the essential amino acids for growth of livestock, poultry and fish. L-Tryptophan is one of the essential amino acids for the growth of livestock, poultry and fish. When L- tryptophan is insufficient, there will be stagnation of livestock and poultry growth, weight loss, reduced fat accumulation, testicular atrophy in breeding stock and other undesirable phenomena. Therefore, tryptophan is one of the important amino acid feed additives. Tryptophan is the third largest feed additive amino acid after methionine and lysine. By adding tryptophan, it can regulate the balance of amino acids in the diet, so as to promote the growth of livestock. With the development of domestic livestock and poultry industry, the application and promotion of tryptophan in feed additives are getting more and more attention.