The small intestine is one of the digestive organs of the body and is part of the digestive tract. The small intestine is connected to the stomach above and to the large intestine below. The total length of the small intestine is about 4-6m, which is the main place of digestion. The food enters the small intestine after the stomach’s elimination, and the bile, pancreatic juice, and small intestine fluid secreted by the small intestine, which contain various enzymes, respectively, carry out digestion, including power and wear, and contribute to the perfect digestion of food, absorb food through the mucous membrane of the small intestine, absorb into the blood, and carry out the nutrition supply of the whole body, which is the main function of the small intestine. The small intestine, as the longest organ in the digestive tract of the whole body, is also the most important place for digestion and absorption in the human body, and is vital to the nutritional status and health condition of the human body.