Abstract: Tree resources are rich and diverse in China, but they has not been fully developed and utilized. The contents of crude protein, neutral detergent fiber and acid detergent fiber in tree leaves are high, as well as the contents of flavonoids and phenols. However, some leaves contain anti-nutritional factors such as tannin and phytic acid. Microbial fermentation prolongs the use of leaves, degrades anti-nutritional factors, and transforms nutrients that are difficult to be absorbed. It is one of the green feed processing technologies that can change the leaves into biological feed with goodpalatability, non-toxicity, low toxicity and high nutritional value. At present, the main types of fermented leaves are ginkgo leaves, moringa leaves, and mulberry leaves. The strains used are mainly lactic acid bacteria, mould, bacillus and yeast. After fermentation, the preservation time of the leaves is prolonged, the crude protein content is improved, and the quality is better. Fermented leaves have higher contents of flavonoids, amino acids, reducing sugars, polyphenols and other active substances, which have strong antioxidant activity. The application of fermented leaves in chicken production can improve the antioxidant capacity of animals, promote body and intestinal health, and improve growth performance and production quality. Fermented tree leaves used for feeding animals are beneficial for resource recycling, which reduce production costs and solve environmental pollution.