Bile acid is the main component of bile and it has important physiological functions. Bile is secreted by liver cells and it has two roles, one, as a digestive fluid to facilitate the digestion and absorption of lipids. Second, as an excretory fluid it can excrete some metabolites in the body, such as cholesterol and bilirubin, through biological transformation in the liver into non-nutritive substances into the intestinal cavity and out of the body with feces, which is also a function of bile acids. Bile acids are divided into two categories, primary bile acids and secondary bile acids. Primary bile acids are directly synthesized in the liver cells from cholesterol and are called primary bile acids, including bile acids and goose deoxycholic acid. Secondary bile acids are mainly formed in the intestinal tract after being broken down by bacteria and combined with sulfuric acid or glycine.