A carbohydrate compound is an organic substance composed of three elements of carbon, hydrogen, and oxygen. From the chemical structure, the carbohydrates are polyhydroxy aldehydes and ketones and their multimers. Sugar is widely distributed in the plant kingdom and is the main constituent of plants. It plays an important role in the physiological and biochemical processes of plants. According to its structure, it can be divided into monosaccharides (including glucose, fructose, galactose, etc.), disaccharides (including sucrose, maltose, lactose, etc.) and polysaccharides (including starch, glycogen, muscle glycogen, etc.). Monosaccharide is the simplest carbohydrate, polyhydroxy aldehyde or polyhydroxy ketone that can no longer be hydrolyzed.