Abstract: Since Mendelson syndrome was reported in 1946， preoperative fasting has become a widely accepted golden rule， but it has also brought about other problems， such as patients′ fear of surgery and strong hunger， even hypoglycemia， hypotension， dehydration and other symptoms. With the clinical application of the concept of enhanced recovery after surgery in recent years， as well as the improvement of the level of medical technology and the requirements of patients for surgical comfort， which can encourage clinicians to make continuous efforts to ensure the safety of surgery while reducing surgical stress and postoperative complications. Therefore， when to fast before operation has become a problem that clinicians need to solve. This article reviews the current clinical reports on preoperative fasting.