Parenteral nutrients include carbohydrates, fat emulsions, amino acid preparations, vitamin preparations, electrolyte preparations, trace element preparations and other components. 1. Carbohydrate preparation: it is the basic component of parenteral nutrition preparation, which can provide 50% to 60% of the energy needed for human metabolism. 2. Fat emulsion: one of the non-protein energy sources, it can provide a large amount of energy, reduce protein consumption, alleviate weight loss and promote the body to restore health. 3. Amino acid preparation: as the nitrogen source in parenteral nutrition, it provides raw materials for protein synthesis, and is formulated with a certain proportion of amino acids, which is the basic component of parenteral nutrition. 4. Vitamin preparation: it can supplement water-soluble and fat-soluble vitamins to maintain normal metabolic activities of human body. 5. Electrolyte preparation: maintain the water electrolyte and acid-base balance in the body to ensure the stability of the internal environment, so that the metabolic activities can be carried out normally. 6. Trace element preparation: trace elements are involved in the composition of body enzymes, used to maintain the metabolic activities of the three major nutrients, will not be lacking in the short term, and need to be supplemented for long-term fasting. The use of parenteral nutritional preparation should be carried out under the guidance of physicians, and should not be used on its own, so as not to cause imbalance of nutrient supplementation and other serious complications.