Background　The preoperative fasting time before elective surgery is generally longer (>10 h) than it should be (4-6 h). Considering the impact of long preoperative fasting time on the health and prognosis of patients after surgery, the procedure has been recently updated.　Objective　To evaluate the safety and benefits of preoperative supply of carbohydrates in the terms of the rapidity of patients′ recovery after surgery.　Content　Suitable amount of water soluble carbohydrate supply before operations, named preoperative oral carbohydrate (POC), promotes postoperative rehabilitation in patients. Accumulating evidence demonstrates that POC compensates the loss of water and energy throughout operations, relieves postoperative distress (thirsty and hungry), maintains body temperature, improves perioperative metabolism, and tackles stress, etc. Preoperative oral carbohydrates, composed of maltose, polysaccharide, fructose, glucose, and multiple minerals, can be rapidly emptied from the stomach, and does not lead to regurgitation. Additionally, POC alleviates postoperative insulin resistance and inflammation.　Trend　POC attenuates postoperative insulin resistance, maintains water-electrolyte-energy balance in the body, and promotes postoperative rehabilitation. Its benefits in postoperative complications need further investigations.