Lactulose is a functional oligosaccharide formed by the condensation of one molecule of galactose and one molecule of fructose via 1,4-β glucoside bond. Lactulose, as a osmotic laxative, is harmless to human body and can effectively regulate the physiological rhythm of the colon. It is widely used in the treatment of constipation in the elderly, pregnant women and children. Lactulose has become a prebiotic additive in food production. As a prebiotic, lactulose can also promote the growth of beneficial bacteria such as bifidobacterium, inhibit the growth of pathogenic bacteria such as salmonella, and restore intestinal flora homeostasis in constipation patients, thus improving intestinal motor function.